I think the point is that you don't abandon gmail right now, you give yourself an alternative, and when you access a service or decide to change something about it or need to recover an email, you change it then (and store the new info in your password manager, maybe mark/rename the old info as OBSOLETE if you have that sort of control), and eventually you've decoupled yourself mostly.
Truly decoupling yourself is hard, and you'll probably be finding old accounts and dealing with them for years, but getting 95% of the stuff moved over the next year or so will likely give you a lot of peace of mind if you're actaully worried about it.
FWIW if you're actually worried about it, you should also make sure your email is through a domain you control (even if just pointed towards a service, or even gmail) and that domain service is not linked administratively to the same account that you use for email (e.g. don't register domain through google and then point at gmail), so worst case you can change the destination service by changing MX records and just swap all your email at once to a new handler (or if you're a masochist or as a last resort point towards your own mail server you admin). Just make sure it never expires (in the end, there's always something to worry about, you need to find the risk you're most comfortable with).
I tired that for 6 months. Fastmails crappy spam assassin bases filtering is a deal breaker. I ended up just pointing it back at my gmail. Just an inundation of spam.
I also found their search (which I rely on heavily) to be a joke compared to gmail.
I transitioned to my own domain plus fastmail years ago, and found I barely get any spam. I made sure to make a unique email per service and barely get any spam, and if I do, I can ban the email address. Helps you detect breaches or spam sales way before it becomes public.
I still have the old gmail account, but almost nothing of value goes through it.
The key is the domain, you don't even need to go away from gmail, but own your domain.
Ideally, you get your own domain and point that at whatever provider you feel like. Should you ever be locked out by a provider you point the domain to another one. If you follow a semi regular back up schedule for email you could even import your existing emails to some providers.
It’s much, much easier to change account details when you can still access the old email. Get your own domain for $20/year and you never have to worry about losing access again. You can always redirect your domain to a new email provider if something happens
It's not as bad as you think. Fastmail has a great import process.
Transitioning to a new email address isn't really that bad. I did it about 15 years ago. Whenever you log in to a site and you notice that it's using your old email address, you go into your profile settings and update it. After about a year you'll probably have hit 90% of your meaningful accounts.
I migrated some family email to Zoho the other day. There's a decent free tier and their email service alone is pretty cheap ($1/user/mo). For $1.25 you can get exchange activesync support as well.
I started my move in November of 2018 according to my Fastmail billing history.
I've _still_ got a few places that insist sending mail to Gmail (mostly sites that don't let me switch email for some weird reason).
I got my own domain, set it up on Fastmail, imported all my old mails from Gmail and set up a permanent forward from Gmail to Fastmail.
Then I set up a filter on Fastmail that shows all mails that were sent to my Gmail address and slowly went through that list and switched from @gmail.com to my own domain.
Now I'm the customer for my email instead of the product and I 100% own my own domain so no single company can take it away.
Truly decoupling yourself is hard, and you'll probably be finding old accounts and dealing with them for years, but getting 95% of the stuff moved over the next year or so will likely give you a lot of peace of mind if you're actaully worried about it.
FWIW if you're actually worried about it, you should also make sure your email is through a domain you control (even if just pointed towards a service, or even gmail) and that domain service is not linked administratively to the same account that you use for email (e.g. don't register domain through google and then point at gmail), so worst case you can change the destination service by changing MX records and just swap all your email at once to a new handler (or if you're a masochist or as a last resort point towards your own mail server you admin). Just make sure it never expires (in the end, there's always something to worry about, you need to find the risk you're most comfortable with).