Why dues knowing Xenos Lore keep me from using their guns?

I am a drukhari player so I went into this game wanting to use their weapons and make freinds with all the xenos that can't stand me but I feel like I screwed up from the get go. I wanted to build a duelweilding pistol user with a big Klevix. I meet the fun sexy pirate Isabela type character that wears pants and she gives me a nice sexy pair of shiny eldari weapons for me to drool over exept there are two problems. The game duesnt let me use these weapons until lvl 23 so she gave me weapons only she could use 🤔 I was missing a few pieces of my build before I could use them. Spoiler I also had anouther feature that would keep me from using them.

I thought being a criminal & operative would be cool then ended up falling into a sniper role. Ok fine but when I meet my grumpy eldari besty we end up competing for the same role. It bothers me that each party member fills their role better than the main character can. Jae is better with duelweilding and Ranger lady is a better sniper. Whatever I will be my best me. Except I finaly reached lvl23 and have learned I can't be my best self. In fact I couldn't be my best self from character creation.

I chose Void born cuz in the psfy grimdark world of 40k where everything everywhere sux why would I choose to live with gravity touching ground like some poor person when I can choose to live in SPACE! Exept it comes with a free Xenos lore. That's fine I want to know about Xenos. I wanted to be a cold trader like Jae. Y the F@&€ dues having the Xenos Lore trait stop me from using Xenos weapons?!?! This is so dumb. Knowing the lore should make me better with their weapons. If anything Imperium lore should stop it.

Tldr: I wanted to build a character to use Xenos weapons but built my character for vibes and accidentally locked me out of using them. Why dues knowing xenos lore stop you from using Xenos weapons.