Judging by what ends up in my gmail, very few people "can deliver to gmail" in any kind of reliable fashion. It depends entirely on how messed up the spam filtering is for individual accounts. The only reason I'm still on Gmail is that it's so entrenched in my life that tidying things up to move is a massive pain and will take a long time (and no, forwarding is not a reliable solution; my experience is that even forwarding from one gmail account to another will invariably cause some mail to go the spam folder of the account you forward from - yes there are options that are meant to prevent this; no they don't work reliably, and haven't in the years I've been using it, so it means one more place to check mail).
Getting started now will make it easier though. I just bought a domain, and started emailing from it and using it for new accounts. I still use both emails, but I always reply from the new one. It's a slow transition, but quite a smooth one (I have email clients that can show an unified inbox).
I still have quite a few a accounts under Gmail, but I'll probably do a full change this year.
Having control of my email is very important for me. Google could close my account for any number of reasons (billing dispute, hacked account, etc), and I would lose my actual address since the domain isn't mine
Absolutely, it's gone from "maybe I should move somewhere" to working on untangling things because I know I have to move.
I do have a very old address that is on my own domain, and though that is currently routed to Google, at least that simplifies things a lot, but unfortunately for many years I was not consistently using that address for signing up to things etc.
