Ascend was fantastic until it went free-to-play and Hi-Rez desperately tried to monetize it.

I would want Tribes: Ascend back again as it originally was, but with good support for mods and private servers. That would make me happy.

The out of the blue update actually fixed the game substantially, but unfortunately it seemed to have been a last ditch effort and leadership at Hi-Rez (which probably boils down to Erez) lost interest entirely when SMITE suddenly became very profitable.

I enjoyed this game quite a lot, I never figured out why it didn't take off even when it was free.

It was hugely popular before being free. The problem was that some basic options for the classes that were strictly better or required for gameplay (the worst offender here is likely the Jackal[1]) were gated behind days of grinding or microtransactions. Newly introduced options usually had some severe balancing issues. The core audience and biggest advocates for the game were people that played Tribes and Tribes 2 decades earlier - they didn't really like that they couldn't buy the game outright and have all the content in it unlocked at a reasonable pace.

[1]: https://tribes.fandom.com/wiki/Jackal

IMO for two reasons, separated by player type. Casual players were turned off by the grind, and experienced players (read: players of former games) were turned off by the dumbed-down mechanics as compared to previous games.

By the latter I mean mostly the decision to eliminate base play, i.e. gens/turrets/invs mean basically nothing because you spawn in your load out. Also, the jetting/skiing physics are kinda wonky, in ways that I think negatively impacted gameplay.

The usual performance problems with tribes games, also the usual unintended difficulty increases by trying to make it "easier".