Bacon Bits
Legend
It has come up in my games. My Ranger started with Heavy Crossbow and Dagger and switched to Hand Axe and Dagger at level 2 if I find a great magic thrown weapon I will switch to that.
So, if it had been "you can switch when you gain a level" instead of "at the end of a long rest" then it'd have been an identical feature for you? Did you switch because of gaining a Fighting Style? Or, rather, you choose Heavy Crossbow at level 1 only because it was mechanically better than Dagger even though you already planned to switch once you got Throwing or TWF? And you're only plans to switch going forward are if you find a magical weapon that's better than what you've got now?
You don't think that's the same as saying you're essentially never changing your mastery? You're not planning on changing on long rests really at all. That's kind of the point I'm making. It doesn't really come up.
Also I don't think it is a bad DM to give random loot or if using an off the shelf product whatever is in the adventure. Rewarding players who choose versatile builds is not being a jerk either.
But, do you think martial characters should have to choose between mastery and magic items then? Do you think that's the design intention of, say, fighting styles and weapon-specific feats?
Furthermore, do you think it's good DMing if you take short sword mastery, TWF style, Dual Wielder feat, and then the DM just shrugs when the third magical greataxe drops and says, "that's what I rolled"?
I don't think it is particularly good game mastering to never curate the results of the dice. I know there are people in the hobby that insist this is the only virtuous way to play the game, but I don't know any game designers that would agree.
Magic items are intended to be player rewards. That's why they're in the dungeons in the piles of treasure instead of in the shops on the wall for sale. But a reward that you can't use is not a reward at all. It's like giving a bachelor a cradle for his birthday and wondering why he's not overjoyed.