I have a backlog of games and decided to watch the story/dialogue cut-scenes on Youtube to get the story without having to go through the gameplay (I got stuck on a boss and didn't feel like grinding more to level). Unless I farted around too much in my play-time, it seems that the story doesn't pick up until the middle of the game (around 30/40 or so hours). I think the story should already be fleshed out more by that hour mark, not starting up. Upon the completion of my viewing on Youtube, I believe the main thrust of the story was dragged out and could have been covered in a more timely manner. I also think the characters seem kind of mediocre aside from the "heart-to-heart" interaction. With that said, I have found myself wanting to play through the game rather than being glad that I didn't waste any more time on it.
The gameplay and open-ish map is like...half the wonder though. I kinda got sick of other RPGs giving tiny world maps and dungeons. A Zelda cutscene-only video would probably the most boring thing to watch ever; but since you play "adventurer" for the entire game you love it for that instead. There's also some good story in the non-cinematic bits; the quests do quite a bit with respect to world building.
I do agree otherwise that Xenoblade is a slow-to-warm-up title. I gave it up too when I was in the middle of school and just didn't wanna deal with it. But now it's in my Top 10 for almost all it managed to do. A lot of that really depends how fast you progress in the title of course since there is so much questing. And while it starts slow, I think it follows a lot of the JRPG story pattern where they sprinkle in bits and pieces of terms/themes/spoilery things you only HEAR ABOUT till it's fleshed out in the end-game (Shulk's visions literally spoiling the next 40 hours of gameplay at least); then you get those moments like "why the fuck does Alvis know how to work the Monado?" or "What's the full story with Sword Valley". The game had a big world with a big story to tell, and [I think it] did its best not to rush it.
Easily though, the story really kicks it into full gear when you're on the Mechonis.
The issue with the game's plot is that the first half is all about climbing the Bionis at your own pace. Compare and contrast to something like Xenosaga 1 where your party is constantly moving to new and different locations for the entire game (except for the Elsa, the Durandal and the Foundations locations), and you're constantly getting pushed forward at the pace the game wants you to take. If things are moving slow and nothing's happening, then you're stuck until you advance the plot enough to trigger the next event. If you missed something and want to go back, hope you saved right before that part and hope you don't have too many unskippable cutscenes along the way. And the only way to double back is to hop into a specific type of Save Point or ride your ship back to the previous town. In Xenoblade, plot happens as you advance through the game, but rarely does the game ever say that you can't go back somewhere and usually that's because your party is stuck somewhere due to plot or because its a part of the Mechonis that just got blewd up.
Xenoblade's biggest problem is that, for as many sidequests as it has, there's not that many (more than most games but ratio-wise to what you encounter in XBC its kinda lacking) that end with a worthwhile payoff beyond getting more Exp and relationship boosts (and you might not want all that Exp since you don't get AP or SP for your efforts and the things that do give you AP/SP scale based upon your level).
Also, the narrative structure makes a whole lot more sense if you think of it as an anime series. The shit that goes down in Colony 9 is the hook that pulls you past the three episode test; Bionis Leg/Colony 6 is the part to tide you over while the show does its world building/cast introductions; The Knee, the Swamp Ass and the Mossy Backside are the monster of the week crap that's unfortunately necessary for what's coming up next; pretty much everything to do with the High Entia is the 'those fucking Elves' arc that JRPGs have more often than not (although they're not even kinda annoying in this game because XBC is just that awesome and because they don't exist to waste everybody's time before their inevitable punking/disappearance off the face of the plot like most cases do) and is the series midpoint where the
game finally starts explaining what's going on and the villains return to the plot; which marks the midseason change up complete with the heroes getting trashed, the subsequent midseason upgrade, the reveal of the main villain for the next plot arc (with a guest appearance by the
game's actual big bad) and the plot twists that change the
game's theme for the rest of the
game; then from there the plot picks up as you finally start dealing with the villain's faction; first by having a showdown with arc 1's big bad who's now demoted to midboss status on Valek Mountain, then by revisiting the Swords' battlefield seen in the prologue, then a direct assault on the villain's stronghold to rescue someone/fight the current big bad that kinda ends badly but the rescue went well, then you hit the 'Village of the Ancients' that have people more in the know as to what's going on than the aforementioned elves were (making their, thankfully minimal, previous asshattery a largely moot and misleading point) while also getting their side of the story, then its basically the Mechonis proper which is treated mostly as a straight up siege while the big battle happens off screen; then you get to the end, fight the 2nd arc's big bad in a proper showdown, then you have what happens in most anime (and usually done badly) that guy who showed up during the midseason change up shows up again, turns out to be the real big bad all along, sending the plot reeling off the rails with powerlevel bullshit and metaphors being expressed with lazorbeemz, and a bunch of other stuffs that are massive spoilers.
The tl;dr is that Xenoblade's plot is what everybody said it was back when they first played it, it focuses on getting the essentials right rather than making itself part 5 of a one or two part series.
How far do you need to get in the game before you have characters friendly enough to open up the Heart to Hearts? I'm on the hand and I don't think I've unlocked a single one, besides the mandatory one with Hermione at the start.
Unfortunately most H2Hs require high levels of affection and consist of mostly unique pairings so you can't just focus on one or two couples and hope to see more than 5. Additionally, some H2Hs require the crossing of certain plot points, the two biggest ones are getting Seven and that endgame clusterfuck I mentioned earlier in this post (basically the point where the final arc starts).
That said, the absolute fastest way to grind up Supports is to fight a particular UM in an Endgame region of Eryth Sea. The dude looks like a horse and has a Spike Effect of putting attackers to Sleep. Stick the guy/gal you want to build up Supports with, load em down with Spike Resistance Gems/Skills, make sure the other guys don't have Spike Resistance at all (or as low as it can go if its someone like Dunban who learns a Spike Resistance Skill), then take control of the Spike Resist guy/gal and have the other goobers put themselves to sleep on the UM, wake and repeat, bail if necessary or if the enemy looks like its about to die then mosey off somewhere and come back with a new set of people and do it all over again. You can theoretically do this when you first get to Eryth Sea but its honestly better to wait until the third arc since you wont have to worry about getting creamed by anything that looks at you funny.
If you don't want to go through all the bullshit listed above (or you've already terminated that particular UM as I don't think it respawns), just fight a pack of red nametag enemies and have Sharla around because you'll want to drag things out instead of actually winning fights (although winning fights have their own perks too).