This is how I feel every time I see an overpowered "prototype" weapon in a video game that works better than the standard version.

Agreed!

There's is a bit of clever game design in Deep Rock Galactic, which I hope catches on:

The default load out for new players is almost unarguably the best possible load-out, for that class, in the game.

As players progress, they can unlock more entertaining while objectively worse equipment, to amuse and challenge themselves.

And, I mean, of course we do. It's hilarious because some truly challenging gameplay emerges.

And when it's kicking my butt, I at least realize I chose that challenge for myself. I had the option to bring the good equipment that I started with, after all.

And it puts new players on more even footing with veterans. I tend to make easy missions with newbie friends harder on myself by bringing truly silly equipment load outs. It usually turns out fine, and when it goes badly for me, they feel good for rescuing a veteran. Or it goes sideways and I apologize and make slightly better equip choices for the next try.

I assume the excuse usually is that the prototype was unstable, so they had to 'tone it down'. But of course, you as the awesome hero man can control it!

It needs a flaw to be fun; there has to be a problem that made it unfit for production and the solution lowered the power. Too inefficient, too inaccurate, too big, too unsafe, too unreliable. Make it a fun thing the player can play around so it's a sidegrade rather than an upgrade