I’m with you on a coaster not being the ideal ride system for Avatar. When it comes to Marvel as it stands Cosmic Rewind is Disneys best attempt so far but that makes sense as it was purpose built and had a very healthy budget. My take is a coaster would be more popular than whatever they are planning for the Avengers ride. Does it allow them to showcase all the characters/ locales in way a simulator would? Of course not but I have no doubt a coaster would be more popular and have the energy and thrill an Avengers ride should have. It doesn’t make sense to me to have the Star Wars and Marvel rides have more or less the same level of thrill as say MMRR. Which brings me back to my original point. If no thrill ride with Star Wars or Marvel then where in your IP library?
For me it’s gotta be the Endor Speeder bike coaster a la Hagrids. That would be incredible.
It's not a general Marvel IP though, they've specifically designed and marketed this as an Avenger's E-ticket featuring Thanos and a smorgasbord of other characters, that surely requires a screen to pull off. I'm with you that the overall IP being action-oriented and more teen/adult leaning is a natural fit for more thrilling experiences but probably not the Avenger's specifically. It's also worth considering that Avenger's Campus already has a thrill ride in Mission: Breakout.
As for Star Wars I'm personally glad they went in the trackless direction they did, far more meaningful for me to be able to immerse myself into that world than try to do another style of Space Mountain with Star Wars IP slapped on it. The drop sequence in RotR is also significantly more thrilling than anything happening in MMRR.