> Minecraft and Roblox both have creative / extensible outlets built in to them
Not at all the same thing as the community-created content of old.
Roblox is an entirely microtransaction-driven experience, you create games and publish them on the developer's platform so you can charge players for things and make money, not because you simply want to create something for people to enjoy. The developer is in full control at all times and can decide to remove your content at any time.
Minecraft is fundamentally a sandbox game but that's also not really the same thing. You can still run your own servers with your own mods on the original edition but that's just a remnant of the past and Microsoft wants to get rid of that as soon as possible so they can force you to play their version of the game where you pay microtransactions for servers, skins, maps, etc. And besides, most popular java servers have their own set of microtransactions, and there's no server list, so generally you either host your own server for a group of friends only or join a large existing server.
Compare all of this to the classic Valve game concept of loading up a level or script editor because you have an idea and want to make it a reality so other people can enjoy it, not because you think "I can make money out of this". You release your content on the internet for free, others download it, load it up on their servers, and it's now playable by anyone in a few clicks. Players open up a server browser, scroll through a list of servers, pick one they like and join, and suddenly they're playing a player-created map, on a player-hosted server, with player-created plugins providing gameplay and general quality-of-life features, together with other like-minded players. The developers had basically no control over this entire process beyond hosting the server list. No (alive) game released in the past decade replicates this experience because it's simply not as profitable as having full control of the game.