Minecraft is really great - I would stop ignoring it and play it with your kid. My two "non-gamer" daughters play it several times a week together. They have done so for nearly 10 years.
On the plus side, we have a great deal of fun playing hide and seek with the morph modpack.
His friends all play minecraft on the Switch, but they don’t have mods so he thinks it boring.
Roblox is a lot more open-ended with what it lets it’s users create, which leads to a lot of violent and not safe for children content, mixed with some pretty aggressive monetization. I don’t have a child, but if I did I’d rather let them play Call of Duty (one of the older ones without microtransactions) than leave them alone with Roblox.
Now that he’s accepted that I’m not going to buy any Robux it’s ok.