This is becoming an important factor in deciding to pick up or invest time in a new RPG. Once it was only a matter of generating player interest (and the GM being enthusiastic) but these days, there's a compelling need to make sure that the system shows evidence of support in Roll20 or your preferred VTT environment. I've been playing a game in Astral as well, which runs rather nicely from a player perspective so far.
For a game to catch the attention of the VTT market it needs to show at least some of the following (for Roll20 for sure, and to some degree also Astral):
1. Can I play this game in the VTT environment with minimum fuss?
2. Does the VTT have character sheet and rolling mechanics support for my system to make it easier to mess with?
3. Does the VTT store/environment provide support that will benefit or directly aid my game? And secondarily, is this support vital to the play experience or optional (but desired)?
4. Will the cost to accomplish this be too excessive?
Take three recent examples of games I have looked at or considered running: Scum & Villainy, Mutant Crawl Classics, and Mongoose's Traveller. In Roll20 I have figured out that there are character sheets available for only one of the three (MCC is not on ROll20 yet in any form), and of the three only Scum & Villainy has any material support in the Roll20 store with an introductory module package (Evil Hat has thrown all in on supporting VTT through Roll20, FYI).
This means if I rely on Roll20 for any of these, then with Mutant Crawl Classics and Traveller I have to figure out how to work the Charactermancer to create a character sheet; for my limited time this is a no-go. For Traveller there is a Classic original edition character sheet, very basic. Although Goodman Games has a basic introduction to Dungeon Crawl Classics in the Roll20 store, it hasn't done anything on the platform for MCC yet, which is a shame. As for Traveller....I suspect there are worlds of complexity in the licensing behind getting official support to any VTT due to Traveller's ownership. I am honestly not sure where Traveller players go if they want good VTT support....Fantasy Grounds?
This pretty much means Scum & Villainy is the only viable option for a time strapped virtual GM. They offer a nice introductory campaign module with support materials for the Procyon Sector and tons of useable content. The fact that the other two games don't even have this basic support is kind of shocking...if I were a publisher of some means and wanted to insure sales of my game stay robust in the market of 2020, getting some VTT representation seems like a no-brainer.
Item 4 in my list isn't a factor with Scum & Villainy....the cost of the campaign pack is $14.99 which is worth it to me to get a game running. But for the big stars (Pathfinder, D&D) it can be a major factor. I will admit, I haven't seriously considered running D&D on VTT because I know if I do I will want to buy those enormously expensive rulebook packages on Roll20, and I already spent that cash on Pathfinder 2E....so damn straight, PF2E it will be!
Astral is interesting in how different it is from Roll20, while still being similar in execution. Their shop is mostly tailored to markers and maps, and doesn't near as I can tell focus on providing you with elaborate module packing or rulebook encyclopedias you can access on the site. I imagine there may be entirely different approaches with other VTTs.....I know for sure I ruled out Fantasy Grounds alone, for example, on sheer cost.
Another factor to consider, one which I imagine is quite important, is how much cost is required for players vs. GM buy in. With Roll20 for example I can subscribe as GM but players do not need to. I am enjoying Astral as a player without a subscription as well, but if either required player expenditures they would stop being viable.