It's going to be very hard for me to answer that kind of question in one post, to be blunt.
I can say... that even though third-person space ninja parkour action isn't for everyone, the skill gate is a bit overwhelming to start out (there's an animation called "100 Days of Warframe" that gives a few hints towards this), the grind is honestly a little insane if you want everything the free or mostly-free way, and that the sheer amount of lore and activities can quite frankly be paralyzing, it is easily one of the best examples of how to do a free-to-play correctly. Luck mechanics and the paid shop are... WAY more separate than most free-to-plays are, probably about 99% separate. Maybe even 100% by now. (They had mod packs at one point, but a normal player will have more mods than they know what to do with after a few missions.)
I've heard Digital Extremes, the developer (you may know one of their other works, Unreal Tournament - Warframe is even FASTER paced than Unreal Tournament), even PATCHED OUT a gambling mechanic on at least one occasion.
DE is also unusually active in interacting with the fanbase by the standards of developers.
More specific questions (such as direct inquiries about the gameplay - "third-person space ninja parkour action" doesn't exactly cover everything) may help give a better answer here.
Ah, the third person killed it for me, I like first person. I've played Destiny 2 before though. Also, grindy sounds eh.