Gmail is an email service. Like the fediverse, email is federated.
By changing your email provider, do you really lose anything? You can still contact your friends, contacts and even various customer suports. You also can recieve emails from popular social media apps. If you degoogle from atleast one Google app, maybe Gmail could be the easiest and least life changing one.
While, Youtube could easilly be one of the most difficult to degoogle from. Not like literally but emotionally. Like deep down you know you can find mostly all you might need on something like Peertube but not all the entertainment media like on Youtube. You will also become a social outcast if peertube is the only app you use. You might not understand channels people mention in day to day talk from youtube or references.
If you use exclusively fediverse apps and sites, Chrome could be almost just as easy to replace as gmail, longterm. However If you use Youtube it won't surprise me that Youtube downgrades your performance and user experience in what ever means neccesary on competing browsers.
And you don't need an account on YouTube to watch content there. NewPipe works just fine for me without an account, so not only do I not get ads, I also get no tracking and still get the content I want.
Changing my email on the dozens of services I use is a giant pain in the butt. I'm planning to ditch my Gmail account, but it'll involve a transition period where I set up a bunch of forwards so I don't miss stuff.
The most difficult one for me is Google Docs because I use a lot of Google-specific spreadsheet stuff, like Tiller integration (I don't use Excel) and stock price lookups.
So other than Google Sheets and Gmail, I honestly don't use my Google account for anything important.
There is a way to create a Google account with an external email address. If you don't have anything tied to your Google original account, it could be a way to access Google tools.