[My view on why Warframe feels repetitive (the 15 minute loop)]

The whole issue here seems to revolve around loops. If that's the case, then PvE games just aren't for you, or rather, PvE games that are seemingly endless. You're better off playing games that has an ending and that is it. You can quit, uninstall and stop playing it altogether. Enter PvP games where you're facing players with unlimited variations in their gameplay. But it's different for Warframe.

Horizontal progressions allows you to unlock quests, weapons, and basically more options for you to play with. These options allows you to explore and experiment, not mindlessly level up just cause you want or need to. I like using a Pandero to unload my magazine on an enemy or a Heliocor so I don't have whip out the codex/synthesis scanner or even use a Boltor simply because nailing enemies to walls feels like pure terror to me. The ranking up loop is normal as playing quests in other PvE games like Genshin Impact or Guild Wars except it's weapons which I reckon is far easier and quicker to level up. 

In a mission, you fail once or twice for the first time playing, but it's not like you're gonna keep failing isn't it? You get better at it eventually and then you can cheese right through it. I get a good laugh when I can complete a mission in 30 seconds just because I can. I also feel amazing when I can beat a boss on my own. You just can't expect DE to change enemy movesets and variations from time to time. Can't expect an Eidolyst or Orb Mother to just alter their playstyle as if they're actual players. WE are the real players here. WE control the game. WE should be the ones changing our playstyle however we want. Instead of using a Chroma with Rubico, why not Volt with Redeemer? Or Mirage with Velocitus? Or even a Rhino with Corvas? These are the things we're suppose to think of in a game like Warframe. Wanna feel less repetitive? Start getting creative. Being contented with one type of playstyle makes the game boring and lackluster. There will be no perspiration without these inspirations. 

I only agree to the bounty missions in Cetus simply because they feel similar to the normal mission nodes we play all day long. There's a capture bounty, an exterminate bounty, a rescue bounty. DE could definitely do a rework on that. I do however, enjoy the Fortuna and Necralisk bounties. They're unique, fun, and nothing like I've experienced in normal missions. 

With that being said, PvE games are always gonna be repetitive. It's up to you to find some joy in them. If you have already mastered the massive content Warframe has to offer, then I can only suggest for you to take a break and try something else. My only issue is the bugs, especially the one that randomly prevents me from using abilities and attacks in a mission.