Rotating game modes - optimize?

TL;DR Are the maps created for rotating game modes/special events fully optimized? Or is there any way they can be developed to use less resources?

For example, I had no problem playing doombots on my laptop last year, but this new doombots (and other modes such as the siege mode) have been very resource-intensive.... or in general, very "laggy" for me.

I'm not here to ask for "GIT bettr comp" replies or "turn settings 2 l0w for ur potato" (because theyre already on minimum). I am just curious if there is/are new developers/new tools/more particles that are not optional and severely slow down the game.

I know riot optimized summoners rift, reduced the polygon count like 2 years ago, so I'm somewhat curious what factors may be affecting the new maps.

Another example: When I launch into summoners rift, it's pretty much smooth. If there is lag, it is slight and I hardly notice it. If i launch doombots/nexus seige/some others, i can't crank out 60 fps and it's not stable at like 30 either.

Anyway all comments welcome, but not looking for "git better laptop" comments :)