I don't think you're entirely wrong, but to me, the difference is that a good homage can stand apart as its own Thing, whereas something that's derivative has to lean hard on the the tropes and trappings of the original in order to be anything at all.
Example: Stardew Valley vs a bunch of really mid/mediocre farming life sims it shares a genre with. SV is deliberately an homage to the Harvest Moon/Song of Seasons series and is upfront about it. But you can still pick up SV and have a great time with it, because it's a well-designed and complete game on its own, regardless of whether you even know HM/SoS exists. Whereas with the copycats, the big selling point is "it's just like [Harvest Moon/Stardew Valley]!" There's not enough actual substance for these games to stand on their own.
Obviously, "quality" is a subjective measurement and all, but I think that's where I would draw the line between an "homage" and "derivative."
When Brood X happened, I think one of my cats thought I was responsible for the cicadas. They kept bonking against our windows and she'd look at them, then look at me and meow. I tried explaining but I don't think she understood :(