Probably speaking as someone who has used nexusmods in the past decade. Their monetization stuff is on the "lolwhat, that's kinda excessive" side of things.
I'm so thankful that Minecraft has developed it's own ecosystem for modding (I don't like CurseForge but it's MILES ahead of NM, and modrinth is great) and did not rely on NexusMods. Try to install a big modpack in TES, Fallout or Cyberpunk without actually paying for the API access, it's borderline insane.
I do believe it makes sense in this particular case. xPaw made it clear in his other half of the announcement that he's been burnt out for years, and a big portion of burnout is being asked to do things, whether you love them or not, for free.
Personally, I just can't imagine anyone paying a monthly fee just to access metadata for Steam games and nothing else. At least with Nexus Mods, you're paying for (easier) access to actual content for your games.