I'm as salty as the next person about the ending of the free custom-domain gmail service, but it did last for over 10 years, which is plenty of time to get double ROI for the time and setup investment of the free google solution, and then the replacement solution if / when google rug-pulls the "free" component.

The equation does change if there are value-adds that start getting offered and used which make it more difficult to transition elsewhere (with docs, gdrive etc. being examples of value-adds for the free custom-domain email offering).