What you're saying is Matt should have told them before the campaign that they should focus their characters on specific things that fit his narrative, instead of players creating characters in a way they wanted to.

I'm saying he should ask them to incorporate some kind of hook (however major or minor) that makes encourages them to explore the broader arcs in the campaign.

Caleb would be a bigger example. There's a lot going on there with him and the war and his place in it.

A smaller one would be Beau, who has the general motivation of wanting to stop corruption, which can be tied easily to a lot of different aspects of a campaign.

There's a lot of ways you could do this. It's not limiting in the least bit.

Should Matt just give them character archetypes in C3?

I think you're just taking what I'm saying in bad faith.

So you think its ok when DMs tell players they can't use combat wheelchairs because heroes wouldn't choose to have a disability when you can heal with Magic? Or that they simply don't want them in their story. Thats ok with you?

This is a strangely specific example, and again it's not at all what I'm talking about. Maybe trying to tie what I'm saying to some kind of bigotry helps you justify how mad I've apparently made you, but you're reaching pretty far my man. You've really activated your gauntlets my dude, just punching at the air.