Like when you used to get the free +7 beam upgrade module for starbases?
The initial beam weapon is the "inaugural" weapon... it's huge, does minimal damage and is, for all intents and purposes, a pretty picture. It's window of use is so small that it's darn near irrelevant. The next beam level cuts the size down by what, half? It's more like an insurance policy... a just in case you get jumped before you have the chance to do anything here's a bloated underpowered weapon you can get three guys to wave around...
I have NEVER used it. Ever. In fact, I usually don't build my first warships until I have the last tech in the first block from whatever weapon flavor of the day I choose. I can't ever remember the AI using it either. Besides, having to research planetary invasion and all that just to make it useful for anything other than annoyance really makes it a non problem...
As to being a "complicated" first weapon... we use lasers everyday. From target finding to surgery to making copies. Successful tests have demonstrated it's destructive capabilities. In space, with minimal interference and no air to interact with, a beam should/could/would be that much better. Plus, don't know about you but, the thought of "miss" projectiles flying all over the place until they find something to hit doesn't sit well. What a day it would be... traveling along nicely, heading for home on leave... until that rail gun spike fired halfway across the system finds a home in your canopy... It's all relative, and it all has pros and cons, real and unreal, plausible and not...
Please to consider it "we have to start somewhere..."