What can I do to stop lag when developing large games?

I like to make my games, well, massive.

That's where the problem starts.

Because the games I make are so big, it gets really laggy. I group and union things together to try to help with it, but it doesn't help much.

I see games nearly/as big as my games, but why don't they lag? What can I do to stop the lag? It's been bugging me, especially because my gaming upgraded work PC is having trouble loading it in, and if it doesn't work well on that, chances are it won't work for anyone playing, either.

I don't think that "anti lag" scripts work, do they?

How do bigger game devs make their games less laggy? And I don't want a generic "try making your games less big lol", because that isn't an option, because what's the point of making a game if you aren't making what you want to make?

1. Set all the parts surfaces to SmoothNoOutlines and the parts material to SmoothPlastic. This can increase FPS (frames per second).

2. Avoid using free models. They can contain a "virus" in them (a fire instance most of the time or motor) that spreads to all parts increasing the server's ping/ms.

3. Too many loops (while wait() do, repeat wait(), etc) can also lag the game. Set the loops wait depending on what the script does or use events such as Changed, Touched, ChildAdded, ChildRemoved, etc.

There is more to cover up but those are the basic ones.