It's really sad because this game is pretty fun to play. I think the ranking system just sucks, and it's really demotivating. Like what's the point on getting the best scores on target scores, which normally are quite old and, they're are painful to play (in most cases). I would like to see a new ranking system like in osu!, but not based on combo. I would like it to be based on the amount of score you got. The more score you get > more ranks gain or something like that, so it's based on skill and not on perfecting the map, which is pretty annoying. This "system" may sound dumb but, I just don't like the ranking system of this game, and if somehow this happens, it would keep me playing a very long time, at least in my case.
It comes down also to the fact that SEGA seems to not have updated Project Diva in any kind, on which this game is based on. Project Diva and MM+ both seem to be dying out again, after a relative period of new activity thanks to MM+ release. Although now we have the problem of being forced to buy MM+ (Denuvo prevents piracy, which limits the influx of new players) for a good chunk of mods (though AFT still outsizes it), instead of just AFT. PPD is directly influenced by this, since quite a few players came in from Project Diva and then come to PPD. In fact Eden Project seems to be the current main driver of new charts of larger charters, where they make the PPD chart and the MM+ chart at the same time. Some PPD charters even port their own charts to either MM+ or AFT (Hiki8man PPD pack, JP PPD song pack for MM+ by Skywind7 and Lumi2).
Also yeah the scoring may need to change to a basis of cool,fine,safe,sad (cool has highest priority) the more notes hit in this range, the better the rank and only then factor in actual points, so that we aren't fishing for holds instead of perfects and cools. We already have scoring based on amount of scores, it's just that holds in some charts are so powerful, you can have 200 cool and 70 fine and the other have 270 cool and still have the 200 cool be first, due to holds. You could be the only one having perfected the chart, but because of holds, you'd still be 4th. But yeah older scores are not the best, it seems to be a cointoss for everything before 2016 or so: either decent (Alice in Musicland is old but pretty good for such an old chart) or just outdated (undercharted most of the time).
Being also limited in controls and being forced to play 4key unless the charter included CSInput in their chart also doesn't help. I myself play 4key, but many players (even keyboard players) play with 8key (eg.: DS4, WASD/IJKL). Then being forced to play 4key can definitvely be a turnoff, PPD should just update to allow for 8key standard.
But PPD in it's current state will always exist as the easy-to-get free Project Diva, because AFT requires a dump and a launcher and some knowledge to get started, MM+ is bound by Denuvo and PPD is just free, here up for grabs, but is also bound that stock PPD is terrible (probably copyright reasons) and requires quite a few mods to get it up to par with Project Diva. So PPD will not die really, rather be like the other Project Diva games: small community, but the community ''exists'', it ain't becoming a ghosttown anytime soon.