For me the beginning was just frustrating.. it's less about the lack of new things (while it still was a bit frustrating at first).. it's about how you get new stuff just to realize you can't build much for some time..

An Example:

You simply progress through the star chart.. on Venus you encounter jackal.. and he drops bp's for rhino. So you go to the market and buy the rhino bp. Then you realize you need more bp's. No problem, let's just do the boss a couple of times. Finally you have all the necessary blueprints to build him. You get all excited. So you go to your foundry and you see you don't have enough credits.. credits are easy to get so it's not a big deal. While you are at the foundry you look at the stuff you need to build your new fancy warframe: Neural Sensors, Gallium, Control Modules, Plastids, Morphics.. hm.. while I have a few plastids, I have no idea where I got it from nor where to get the other stuff. So you search the Internet. You approach the Wiki -> Huh.. guess I need to go to.. uhh.. mars, saturn.. and neptune.. alright.. let's see where that is.. approach navigation -> realize you have to go through another planet to get to mars, go through 6 planets to get to saturn and go through 8 planets to get to neptune.. since in the beginning you don't have any idea on how to move appropriatly through the map and you open every container and kill any enemy that looks at you. So a mission takes 15-20 minutes instead of 5 - 10.. and you think about if you are stuck with your current frame (the starter frame) until you actually hit saturn/neptune.. which in your mind will take a long time.. you probably know that you will get other bp's for other frames, you expect that it will take mostly as much effort to get those as it takes for rhino. So you realize that people say that warframe is super grindy. At this point many will lose interest.. I had a couple of breaks during the beginning. After my first warframe (which was valkyr) I got hooked.. (I didn't actually wait till jupiter, I got 75% off and thought fk it..)