10+ years ago I payed a small fee for life time account with them, and they very were good, but they just never made any improvements to their service and gmail just got better and better to the point it seemed ridiculous to keep using fastmail.

I've observed the opposite. They constantly make improvements to their service.

They've got boatloads of features and they're getting better all the time.

When I did switch there was a bug in the forwarding that resulted in some of my emails not forwarding (although this went away and only happened to 3 emails).

They might have had better improvements for accounts that required continuous payment, but certainly not mine. It obviously got surpassed by free alternatives.

Despite this criticism, I am very satisfied with fastmail, they served me well for a long time.