Both auto-forwarding and auto-reply are paid features, which makes cancelling & switching much more difficult. Gmail is a breeze comparatively. I highly recommend against using their addresses (e.g. protonmail.com, proton.me, pm.me)
Email forwarding is available for everyone with a paid Proton Mail plan.
(source)
I don’t think the OP is saying to switch to gmail. They’re saying if you think switching from gmail is hard, just wait until you have to pay to forward all of your email if you need to move away from Proton mail if they end up being as bad as Google. They’re saying use something else that’s neither gmail nor proton mail.