We keep dev/staging/prod in different accounts, and we host some special environments for customers which is in separate accounts as well.

The only reason you want to do these things is for security and liability purposes. They are not an advantage for organizing things, but rather they protect against accidental resource deletion and unauthorized / unintended access.

It’s cumbersome to manage many accounts, but that’s a feature, not a bug: it’s intended to be difficult to switch between accounts, so that you can’t accidentally fat finger the wrong button.