But we did get more than we had. Now it's a formal, indefinite agreement and not even Greenlandic sovereignty would legally change that. I think it's unlikely but you can imagine a world in which this agreement doesn't occur and then Greenland for purposes of financial gain hosts, say, Chinese ports or dual-use infrastructure. Without an invasion or something we would probably lack a legal recourse, whereas now we can point to some piece of paper as justification (as all countries do).
If nothing changed, then it was a good thing that we formalized nothing changing.
It's ok to just admit that the US got concessions from Denmark here.