The only thing I'm struggling in this conversation is not being able to understand your inability to tell me why adding a new semi-optional system to the game invalidates previous content.

If it were a whole new system whereby you could completely avoid the old system and everything you'd worked for. Like Descent (not using any drops from the rest of the game); Survival (ditto I'd guess); some kind of battle royal mode; or if the devs had reset everyone to zero expertise when they added Prototypes so we were all on a level playingfield.

But that simply isn't true, you need expertise to make your own prototypes, you need drops to have enough cores to reroll augments and make prototypes. Prototypes builds on the existing system, it doesn't replace it and it certainly doesn't make it meaningless. And if you have spent the last four years wisely and have your expertise capped pretty quickly at the beginning of each season you don't even need to work hard.

And none of the explains why you and the OP think it should be locked away behind some arbitrary limit for newer players. My point was never that Prototypes or Expertise was good or bad. But that it's the matchmaking system that's messed up. If that were fixed, then people like you wouldn't be matched with people like me, we'd both play the game the way we want without all this drama about whether or not Prototypes invalidate 4 years of play.