I guess at that point for me, it was collect everything and reach MR30. Max out every Syndicate, collect every free Operator cosmetic, every arcane (still working on that), etc.
Warframe is a game of farming, so I set farming goals.
I think for me it's the disconnected "home" hubs and the irrelevance of the dojo and Dormizone. If I could make my dojo a home base, with quarters and crafting and everything there, it would make more sense for a squad to operate from there.
Same with the Dormizone. What is the point of having quarters that you have to go out of your way to visit when you can't do anything there but decorate? I love having more space to decorate, but it needs to be a place I can live and work from.
This was my favorite part of TNW, for those exact reasons.
But I love stealth play and have been frustrated that Warframe doesn't reward it.
While the Ostron standing seems mostly obsolete, you're going to need Rank 4 gem blueprints from Old Man Suumbaat to build amps and other things (Rank 5, he's basically just cosmetics.)
Frost is a highly under-rated frame. I don't understand why he's disliked so much. His 4 will do full armor-strip and is a great CC for headshot kills. Someone conscious about where they're putting bubbles doesn't get in the way, except for people who think they need to be the one to shoot everything on the map, even if there are teammates on the other side of the defense point who can do that.
My only complaint is that his 1 or 2 are somewhat redundant with the 4 when you have a lot of energy, but Helminth can take care of that. I like his 1 for immobilizing high-damage targets, though it became less useful with the Eximus rework.
Steel Path mobile defense, or excavation, Frost is my guy. If only I could freeze the defense target guy and make him quit wandering around. I still often take Frost for defense and just keep moving my bubble.
As noted, you still have to defeat it, but if you want the weapon type, but not the element, the element can be changed by getting the same weapon type with the element you want and fusing the two weapons together. (Which also boosts its percentage bonus.)
Seriously, I told them not to buy a Prius! Those are seeing so much part-theft. The guns won't be hard to replace, but the catalytic converter is going to cost 'em.