I think they're complaining that Lemmy uses the older method of blocking instead of the more modern version.
The old way of blocking is that you don't want to see a person, but they're still free to do what they want. It's just not shown to you. So they can still read everything you post and downvote or reply to it as they please.
The modern way is to prevent the blocked user from interacting with you at all, including seeing your posts.
I don't use Lemmy, so I don't know which it uses, but it sounds like OP is arguing that Mastodon uses the latter but Lemmy uses the former. Reddit used to do the former but eventually changed to the latter.
And even then, the only reason Steam ended support for Windows 7 was because it's an Electron (Chromium) application. They decided to upgrade their version of Electron, probably to take advantage of newer security fixes in Chromium, which forced them to drop Win7 support because Chromium already had ended support for it.