Yeah, that is what I would like to see as well. Let the GOG-Staff focus more on ensuring that the games run in the long run (keeping their games maintained to ensure longevity). Or in other words, it would suck that there were games on the GOG-store that simply don't work on newer machines because the game is old. The ability that games bought on GOG run so well is one of the huge plus-sides of the company. Steam and itch.io don't have this sort of quality control, which is a huge downside. For instance, if you want to play Legacy Freespace 2, the original Steam version is utterly depricated while the GOG version does run fine. Same goes with Total Annihilation.
As long as the GOG Staff have a steamlined way to ensure compatibility with older games (either by using a emulator like DOSbox, a VM like ScummVM or a API replacer like DXGL or DXVK.) I fully like your approach to things. With these three types alone I've managed to make even the most broken older games run on modern graphics cards that don't like some older games within just minutes. I'm sure that GOG can ensure compatibility with older games even faster than me.
Yes, as your argument can't be any more obvious considering last year we've seen the release of Warcraft 1 and 2 and Diablo+Hellfire on this store. These games quickly became the bestsellers on this platform for months. Catering to the audience by selling high-demand games towards a certain demographic is a old and trusted way to bind any costumer even further.
However, I do argue that adding more variety helps GOG in the long run. Remember that these games aren't like a Supernova - they don't appear on the store just to evaporate a few weeks later. GOG Staff and the users expect these games to basically be forever on the store, which means that sales and site-interest will increase over time because people buy all sorts of things, even those games that "nobody" knows about. Also note that not man people write reviews.
What I mean is, the more games are available on the store, the better it is for both the company and the costumer, no matter how demanded a game is. Of course highly demanded games and "unknown" games aren't perfectly equal, but it doesn't mean that both don't deserve to be DRM-free.
I do agree that GOG should sometimes cater to their core audience and release a highly demanded game if they can, but not always. I do believe that GOG should become more open to all sorts of games, not only would it make these highly demanded games stand out further, but it would also ensure that people who like variety will get their fair share in the long run as well.