Here's the problem - after a certain point there is no challenge at all to any of the new game content. I hit the point a long time ago where most of the level 1-40Ish missions on the star chart cannot deal enough damage to kill me unless i stand still and do nothing, and even then with armor and dr they might not be able to manage it.
So from there you go to steel path, right? Enemies get +100 added to their level, tons of extra armor, health, and shields.
So what does that mean? Will, a lot of grineer enemies have something like 90+% damage reduction from armor so to kill them you need a gun throwing out at least five figures of damage, if not six. Same with corpus bc you need to get through their massive shields.
So you basically need to rip a gun off of a star destroyer (ironically your actual space ship guns for fighting space ships in space cannot be modded to do enough damage to reliably do steel path without blowing through their very limited ammo in a minute or two) to do enough damage. Unless you have armor strip or defense strip. Because then your anti-tank rifle is back to ohking everything like it does on the level 30 content. So now the challenge is mostly a few special enemies that have mechanics that prevent them from being ohk'd by any means, and that enemies throw out so much damage that some of them can drop your shields in one shot them kill you with the next no matter how ridiculously hi you pad your effective hit points with hp, armor, and damage reduction. So to survive you have to abuse a mechanic where you get 1.3seconds of i-frames when your shields drop, or a mod that gives you i-frames when you roll. Is your frame's theme having lots of armor or hitpoints? Doesn't matter, there's no amount of hp that will keep you alive and the frames that don't have shields at all bc of massice hp are mostly useless. Even capped out Damage resist won't stop you from getting two-shot at a certain point, you must use hard cc, shield gate abuse, or dodge i-frames to stay alive. The game turns in to rocket tag where you one-shot everything with weapons through out sic or seven figures of damage but anything can 2-tap you. Tons of warframe abilities become useless because they just don't scale high enough. A skill that strips 50-75 percent of an enemies shields is great for all normal content, but in the really late eng game where I'm largely stuck enemies will still have incredibly effective hp and dr.
It's very frustrating. There's been enormous, enormous power creep over the years to the point that there simply is nothing that could be reasonably called balance. I play a frame called Trinity and one of her key abilities is being able to restore mana to the team. Well, thanks to power creep, not only are there half a dozen frames that do team mana regen better than trinity (remember this is one of her core abilities as a support caster), but there are now multiple ways to get unlimited free mana that don't even rely on your warframe! so now any punk ass on the street can do one of the most important things my class/warframe does, often better. And that sweet sweet 75% damage resist that trin can give the entire team with her ult? Fails to scale and falls off drastically in the late end game.
It's so frustrating. And you don't even need to necessarily do the hyper meta bs, bur if you don't you're going to get left behind by players who have ultra-mixmaxxed gear that can clear entire rooms in seconds and lay down hard cc that incapacitates every enemy currently spawned indefinitely.
There's a mode called "sanctuary onslaught" which is basically a horde mode with endlessly scaling enemies and people farm it by building a frame that can stand in the center of the room and ohk every enemy on the map by just casn't their 1 or 3. And it's not just one frame, there's like half a dozen that can do this. So there's no gameplay in this horde mode. You just stand around with your thumb up your ass bc the nuke frame is killing things as fast as they spawn.
I really like warframe in theory, i've been playing it on and off for ten years, but the totally unfettered power creep is so frustrating.
steel path really does feel like every enemy is a bullet sponge unless you have a min maxed build. The circuit sucks because all of my frames are not steel path ready lol. I do feel my play styles are restricted under steel path, like you said too many abilities just don't work and where not meant to go up against that much resistance. you can't really play as anything other than the top tier frames like mesa and sayrin unless you learn to abuse mechanics. I hate games where I have to abuse mechanics to keep up, kinda just takes me out of the game. I have been able to get by avoiding steel path, but the circuit and encarnon stuff kinda forced me to try to work it out. Although I think I play warframe more for all of my shiny primes more than for the gameplay at this point lol.
I really think they should never have put actual loot in steel path. Just let it stay as the stress-test mode it started out as, with lots of cosmetic and bragging rights rewards instead of having actual gear locked behind it.