My sons are now almost 18 and almost 15. They both played Minecraft and Roblox and I do consider them to be educational. As sashh says you can use Minecraft to build logic gates.
Ds2 has built some incredibly complicated systems within Minecraft basically this is electrical circuits, self watering farms, self harvesting stuff, huge automated systems. He now uploads videos onto YouTube to help others understand how to do some things.
Roblox does have some crap stuff on it but also my two played the game where you get "jobs" and understood that you build your skills to get better paying jobs, that "money" that you earn allows you to buy things for your "house" that again you buy or rent.
Tik Tok is something I wouldn't let her on at 8 on but Minecraft and learning the names of gems, understanding how you craft things together is learning something. ie you get a log from a tree, you put that onto the crafting table and it turns it into 4 planks and then you turn the plank into sticks. Take 3 planks and 2 sticks of wood and you get a wooden pick axe. Mine stone with the pickaxe to make a furnace, then you can heat iron ore to make an iron ingot which makes an iron tool.
But this is about balance between games and everything else. At no stage have I ever paid for anything within a computer game, my sons spend family time with us, we watch tv or play card games or board games.
Just because you have a device doesn't mean they have to live on it. Give them set times to be on it. The rule in this house was if you complain about coming off you lose it for a day. Obviously my children are online more as teenager but if I come back from the supermarket the second I put my key in the door they are off their computers to help bring the shopping in and put it away.