I've got 5k hours in this game I've done all the builds that matter from the powerful to the stupid there really aren't that many REAL options for building in Warframe. You don't really get more build options the higher you get, you just start to realize how much of the arsenal is just worse versions of each other with not many unique things to them
And the silly builds I'm doing are 1 million overguard rhino death knight sevagoth my old Oberon build took 3 just for the funny wisp has 2 because wisp and now her prime is out years later my nezha build which is very similar to rhino inaros also another funny number build kullervo angry about his overguard just sucking so much he needs it and a few other build.
I don't need Umbral forma actually I have a mag build that's lasts 3 hours in SP mot without a single umbra mod Warframe is a power fantasy game that is exceptionally easy once you pass Mr 14 if you know what you're doing. The problem lies within artificial scarcity the only thing holding me back from having more fun and playing more is that I don't have Umbral forma to do all the dumb builds I want on different Warframes that aren't mag room nuke level.
I could make the argument that no one even needs forma and you just need to get good scrub pick better gear but that wouldn't be fun now would it ?