Grinding is kinda what you do in Warframe. Grind for rewards, grind for better weapons, mods, warframes, etc. And yeah, you have the option to skip the grind by paying plat outright but for the majority of the time you will be grinding.
I honestly like grinding because it makes me feel like I've put in effort for whatever I'm trying to get rather than it just getting handed to me. Not to say that I will grind for hours on end, I get extremely tired of it lol. Just take breaks, step away from the screen, and come back later.
Grinding is definitely not for everyone and it really sounds like it's not for you, so I hate to break it to ya but this game probably isn't for you, then