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.
I had a similar history but I went through the process anyway. Got my own domain and used Fastmail for hosting. I like their masked email address feature. It’s taken months but I went through one by one and changed all my important email addresses. There are a few that can’t be changed though, and some services that I signed up with using my google account also can’t be changed. It was still worth it. Calendar isn’t a big deal to change either. I forwarded all my email to Fastmail and also subscribed to my google calendars to make the transition easier.