Once you go Foundry you don't go back has been my experience. PF2 is not an easy game to forgo the automation. There are many an RPG that are tho. So, largely its going to rely on how heavy the ruleset is. Yes, naturally D&D is going to get a lion's share of the development. It is also difficult to go back to crank windows after having powered ones. For example, I find roll20 nearly intolerable now for a number of reasons.
Another point for Foundry is being able to do the work yourself, assuming you have the time and skill set to do this. I feel like Foundry will become the VTT set of the sleeve rollers. A lot of that work will roll down hill to folks who just want to use it. Though, you will need to be patient. Of course, many folks will just toss cash in the air and say "just automate me bro!"