Everytime I get into a rhythm with Warframe and start having fun it plonks down a RNG blocker of some kind. I'd be fine with it if it was just reasonable grind but whenever I need to get the gateway things to progress I always need some kind of material or some kind of loot drop. It's so blatantly obvious that the aggressively tedious grind is there to encourage you to spend money. Which is why I hate when the shills for Warframe say the game is the "fairest" free to play game. It's not. Free to play games are inherently anti-consumer. I'd rather pay £50 full retail price and get a cosmetics store. With nothing locked behind bullshit RNG.
Okay, well, here's the thing. Warframe is like a game under constant development. I remember at first launch it was barebones, definitely a grind, dropped it. Came back to it many years later, a lot more content more mechanics polished etc.
So Warframe is a bit weird in that you have to set aside your previous impressions of the game if you left and came back lol. What used to be a grind may not be so much a grind now. While the RNG is still there, the trading system is well done so you can make platinum, simply selling mods, or what dupes you get, or whatnot. And then you can trade that platinum for someone who probably has the part you need.
In essence, you're taking advantage of players that throw money into the game...
Because things everybody wants are RNG for the entire population. Sure, you can buy weapons and buy warframes, but you can only trade Prime parts. Which are RNG drops. For everyone. Which is very.. surreal. Now, of course this means time spent trading. Luckily, the player community is pretty damn proactive and there are multiple sites where you can just list what you want to sell for how much and all a buyer needs to do is copy&paste the /t Would like to buy XXX from Warframe.Market for YYY.
Warframe is a weird game that's always in development process (and not in the manner of separate expansions). So you kinda have to get a new impression every time. Like I said, I dropped that shit like it was hot when it first came out, how many years ago. They're working on a new melee system, actually; If you've played Space Marine, the concept of its smooth-switch between melee and ranged is mostly implemented.
Almost all F2P games are not exactly "free," of course. But, as always, there are exceptions (or rather, almost any genre/society/entitty is 99.9% shit with 0.1% outliers).
Marvel Heroes Online was a brilliant F2P diablo-like. All ~50 characters had unique mechanics and talent trees. There was ingame currency drops that you could use to buy characters, aka free. And they'd throw massive sales IRL so you could grab a character for like a few dollars. Or a costume. Indeed, there was no in-game benefits from paying $$ besides temporary xp buff or whatever.
And then it imploded because of change in management, the new people wanting to "consolize" it. Someone else can detail the specifics, but Marvel Heroes Online literally went Offline immediately after that rearrangement. Very sad.