You can always squash the branch before merging back to master.

You cannot avoid this, only can parcel the cost and accept more breakage on the way.

With a big merge, others have time to inspect and know of breaking changes. with million tiny merges (or working on trunk, same) you either freeze change due to risk of breakage or end up with broken master regularly.

Only if you don't know rerere, and don't use it immediately after updating master. I carry tons of feature branches with me, which are automatically rebased. Only once or twice a year I need to fixup things a bit, and those things are the things I immediately worked on, so I know for sure how to merge it. Everything is scripted.

If you let them stall it becomes a mess, sure. If do it properly it's trivial.