While I wouldn't mind a fourth Kelvin Timeline movie, I wouldn't mind if TPTB decide to do something different either. As with the case with the original four TOS movies (1979-1986), the Kelvin movies filled a hole when there wasn't any new Trek on TV. With the abundance of new Trek shows on Paramount+, a case could indeed be made that the need for new Trek movies isn't necessary--but new Marvel TV shows on Disney+ isn't stopping the production of new Marvel movies.
Personally, I think the key to any new Trek movie is to make it a special EVENT--something you won't see anywhere else. It could be a particular cast (Kelvin or otherwise), an era that Paramount+ hasn't explored yet, or something so game-changing that it makes everyone take notice.
The alternative though could be to do the exact opposite of the above, and forget about making blockbusters altogether and make future Trek movies essentially two-hour TV movies that could be produced on modest theatrical budgets and with equally modest marketing. Such movies might have to rely less on spectacle, extensive location shooting, and feature smaller casts, IMO. Such movies might also have to adopt a dual release model of a limited theatrical run and streaming on Paramount+ possibly.
I agree with much of what you're saying, though I do think there's a difference between what Disney Plus and the MCU is doing versus Paramount attempting another Kelvin movie or even attempting to emulate Disney. It would almost be the reverse.
The Disney Plus series are providing connections between the films, introducing new characters/storylines, while also giving some overlooked or underused characters a spotlight. Paramount could do the same with the Trek (and already was ahead of Disney when it comes to the TNG movies and DS9/VOY, and to a lesser extent ENT and Nemesis), but the big difference to me is the massive success of the MCU movies and how that's driving a thirst for more content. Unfortunately, the Kelvin films ended on a whimper, and while Trek is expanding again on the small screen, and Kurtzman Trek is seemingly a success, I don't feel it's the kind of success that the MCU has, or perhaps even the rabid fandom that made the Snyder Cut happen.
There's nothing wrong with Paramount trying to get there, but I don't think DISCO, PIC, Lower Decks, or Prodigy are even on the mass audience level of popularity of TNG when it jumped to movies, so I don't know don't how well a theatrical release of a film connected to them will go. It could be a debacle like the Firefly movie Serenity, where the studio mistook internet love for mass audience acceptance.
I don't know how much general/mass thirst there is for Trek, especially compared to the MCU, or that the streaming series can generate enough of it to warrant movie spin offs. That said, the idea of a cheaper films (the old model for TOS and TNG movies) I think would be more the way to go, but then again, none of the new Treks are as popular as TOS or TNG. I wonder if the hard numbers would have them getting the viewership of DS9, VOY, or ENT even. And if it's as I suspect, I would rather they do event streaming films like HBO Max is doing with Batgirl. Do a crossover event like the Arrowverse instead of trying to compete against Star Wars, Avatar, the MCU, and DC.
I thought the Short Treks were an innovative way to explore some unexplored or little explored corners of the Trek franchise and I wouldn't mind seeing more of those, or even movies along that line that are exclusive to Paramount Plus.