I completely agrees with you, and I feel the reason is behind the current trend in the gaming industry, which is basically getting closer and closer to mobile games, like you know things like Candy Crush, or more extremely, the casino-type games. These games appeals to the most primal part of our brain: winning the lottery, finding a rare gem randomly on the ground etc., basically getting something good by doing nothing, even if you already did that same thing for 50 times before without getting anything. Many research showed that "reward after random intervals" is the strongest way to reinforce a behaviour during training.
However, Warframe also boast some of the best visual and art designs, as well as world building. So it also appeals to our desire for beauty and creativity as well, and attracts people who likes games with rich stories and beautiful sceneries like Baldur's gate, old Bioware RPGs etc. Essentially, there are many different types of Warframe players, and although we all play the exact same game, if you look at what we do in a game session you could totally think we play completely different games. One person may run 1 minute Void capture for 50 times, crack the relics he got in a Void capture fissure and promptly sell those prime parts he got, buy a riven then log off. Another person can spend 20 minutes looking for secrets and details in the new tileset, getting some inspiration and proceeds to create some super creative dojo decorations for the next 3 hours. Someone else might spend 2 hours soloing the secret hard mode boss with an MK-1 Braton and normal Excalibur.
Suffice to say Warframe is trying to get the best of both worlds, but it is indeed one of the closest game to actually getting there.