I have two young children, a boy and a girl. They both love playing Roblox, and I play along with them too, and their friends join in as well. Yes, they both always want more Robux, but let's look at this from a different perspective:
They create their own worlds - often amazing, it's not like they can run out of LEGO pieces, their creativity is their only barrier. In COVID lockdown, they could carry on playing with their friends, despite not being physically together. Humans still monitor and care for the "game", yes, some bad actors might get through occasionally, but on the whole, it's a safe and well-controlled, fun place to be. I used the concept of a Roblox Avatar to gently explain to my children, that people online might not be all they pretend to be - after all, in some games, I'm a super weight-lifter with a six-pack, and I have wings too :-O We all laughed. It's already taught both my children some genuine life-lessons - working in a pizza shop and doing deliveries, earning money, deciding how to lay out their dream houses (and Theme Parks!), and so on - plus, the importance of locking the door to keep the "bad guys" out.
All this, whilst having fun. Roblox is a force for good - if you pay the odd time for some credits, then so what, developers and us creatives also have to keep the roof over our heads.