Hello,
Warframe have huge amount of weapons. It does not help the fact that there are also rivens + non standard approach to status compared to any other games out there. This makes very hard to create, or even think if specific build make sense (especially for inexperience people). The only way to test weapons is simulacrum, but it's used only to spawn enemy. You cannot "truly" test weapons, because you are blocked by weapon's mod slots (polarizations).
This is bad, like very bad that you need first to spend time to farm form, and lvl up again weapon just to test one build. Your build is bad, or want to check if it's better? Then go farm more forms and again lvl up weapons to test another build. Previous one was better? Then go far more forms and again lvl up weapon. I know Warframe is grind game, but c'mon, we grind to collect, not grind just for the sake of possibility to being able to experiment.
This approach discourage to try new weapons. What's the point of so many of them then if game won't encourage to use them? From what I've observed, people usually stay and use same weapons for majority of time, partially because they are discouraged to try new one. I know there are Rives mods but what's the point if again, you have no way to test it?
Why simulacrum can't have free methods to modify mods for testing purposes? Right now simulacrum feels like waste due to only spawn enemies (and not even all enemies from the game).
I know that there is https://overframe.gg/ but this only gives you raw data that for many won't tell in practice if gun will be good. Especially taking into consideration that game have several fractions which different weakness and strength + there is also attenuation thingy + there are also warframe abilities to take into consideration.