What's wrong with Minecraft? I'm not exactly a Microsoft fan, but am pretty impressed with how little control they have so far exerted over Java Edition, they even made modding easier recently by removing obfuscation. You can run your own server as much as you want with no fees, obligations or anything. And unless the kids know a server address, they can't easily join some third party server with weird stuff going on. Not that I ever heard of one of those, but I'm sure they must exist.
As others have said there's a big difference between the Minecraft "we" (the tech community growing up on Beta versions of Minecraft) know and the Minecraft of today.
The subsequent versions also developed the game mechanics a lot to turn it into something closer to an RPG than the early, bare-bones sandbox game with minimal, well-understood mechanics and the rest purely up to the players' creativity.
There's nowadays an abundance of Pay-to-Win servers with custom mechanics to enable that, and I'm sure a lot of unsavory people preying on children. The social media (YouTube/etc) community around it has exploded too in a way I don't recall it before (I used to be into Minecraft videos back in the ~2012 era, and what I see nowadays grosses me out in comparison).
Java Minecraft (the old version, moddable, self-hostable) and Bedrock Minecraft (windows/console only, no self-hosted servers) are quite different.
The sad thing is that Bedrock is super simple. You can get it on any tablet, pay like 5-6€ a month to Microsoft for a "realm" and you can play with 3-4 friends online. They can join even if they don't pay, any mobile device, console or windows PC will work.
With Java you need someone to host the server or pay for hosting, then you need to give the address to your friends and have them connect. Then you need to worry about whitelists, because there are multiple services scanning for open Minecraft servers and people WILL come in and fuck your world up (happened to me).
Roblox is a dystopian nightmare in comparison.