I liked the Grineer missions where your squad could complete different objectives in parallel/spit the squad up to perform different tasks, and the missions also felt somewhat unique compared to the base game. Corpus missions on the other hand just feels like playing a mission to play some other game mode already available on the base star chart.
I don't like the current energy system for ship abilities, it feels like it was balanced poorly because it's dependant on which warframe you chose, and feels like certain warframes were nerfed before the system was even implemented. Energy costs scale poorly with Hildryn, she was nerfed before the update dropped because people wanted to make use of Shield regen for casting abilities. If I remember correctly, this was also part of the reason Dispensary's duration was nerfed as a Helminth ability when the helminth system was added.
Current combat in space is an improvement over what we had in early versions of railjack; if the host had bad weapons for their railjack you had to put up with it because enemies heavily resisted archgun damage. The Amesha was and probably still is the only usable archwing for these missions. Gunnery 10 still feels like it's a nerf, I just prefer the feeling of having control over what I'm shooting at and not that it's automated for me, the extra overheat on top of that doesn't help either though. Other people might appreciate the lock-on, but it probably belongs under an accessibility setting rather than the last unlock for an intrinsic.
Not sure if void fissures ever changed, before if you were moving too fast through the level, you would just hit multiple void fissures and die. I think they might have just been spawning them directly on the player as the tiles loaded.
Overall, I think most of the game mode needs a rework and other game modes to differentiate it from the base game.