So, sometimes enemies do attack waves where they drop a bunch of photon cannons, sunken colonies etc...

They drop them right in front of my walls, and so when something dies my drones will not replace them because it's blocked by the enemy building that's 10+ tiles away.

This also prevents using turrets to clear enemy bases most of the time, as the enemy bases also prevent you from placing buildings nearby.

Is this intended?

My mod doesn't limit on how you place your building.

Do you use AAI programmable vehicle mod? It's likely caused by this mod. It has a feature that prevent you placing building near enemy building.

Try set "Deadzone construction denial range" to 5 tiles or something low. It default at 50 tiles.

That fixed it, thanks.

Two other questions that have come up.

Is there a way to set the worlds enemies to 'mixed' for Space Exploration, so that all of the races are there?
And is there a way to reset more than just the vanilla biters level? It doesn't want to reset for toss/zerg, and I may have created a ribbon maze packed wall to wall by mistake. I kind of got back into factorio after a long time away and threw a bunch of mods together, and then set enemy base size to max and minimum distance to minimum. I have a legion of AI tanks helping me push, but I'm running extremely low on copper and am barely making a dent lol.

I tried to reset enemy level with a different mod, which is probably why the biter reset worked.

"Is there a way to set the worlds enemies to 'mixed' for Space Exploration, so that all of the races are there?"

ya.. You set that in the map generation method setting. "Default" mix all enemies together. "1 Race / Surface" will random pick a race when you discover a new planet.

"is there a way to reset more than just the vanilla biters level?"

There is a way to set to a higher level in in-game UI. The mod don't have function to reset level from the UI. You can reset evolution factor, but that's different from the level.

"I tried to reset enemy level with a different mod, which is probably why the biter reset worked."

I have no idea what you did lol.