protonmail is great as a secure disposable email, but as a go-to daily email service I found it too difficult to manage. Hard to use other email clients due to requiring this bridge, and their mobile apps and web guis are just not up-to-par with other offerings. Being able to use any frontend on mobile (and not deal with complicated proxy setups) was my biggest issue.

Using a custom domain has made the switches easier, as I don't have to tell anyone to update their contacts or worry about forwarding. Just exporting/importing, change some MX records, and I can switch providers any time.