they purposely give you s***** blueprints in the hopes that you get pissed off and rage buy more 

It doesn't make me want to buy things, it just makes me want to stop playing.

Blueprints, or lack of

Does the game just straight-up stop giving you blueprints for the mechs and guns you own after a while, to force you to use other ones?

I'm consistently opening 2-3 crates after every game, plus the usual extra blueprints from events etc, but its been *days* since I actually got anything I can use.

BMChris, Mech Arena features a lot of Mechs and Weapons hence there are a lot of various blueprints to distribute. There are no certain patterns in accordance to which the blueprints fall from the crates - the contents of the crates are random and so are the blueprints that you receive.