My 2 cents.
If you really want to make a 3d mmo game engine that has a market.
Look at 2d engines like the ones here, construct, and clickteam fusion.
If you can bring simplicity without giving up creative freedom to a 3d environment like they have done for 2d, you will have a marketable product.
The trick is to study how their coding systems work without programming and use a similar logic, but using 3d. I've tried blueprints, and I like Unreal, but if I could program a 3d game using tools like those in fusion and contruct, that would be worth years to me.