https://pioneerspacesim.net/ Although, after watching a few videos on how to play it, felt an itch to play Elite Dangerous. So haven't played Pioneer much.

What do you mean?

you can put down buildings while on pause.

Now this! is a pro-tip. Thanks!

There are definitely some maps on the new planet where I seemingly realized that pausing was strictly necessary as the waves start overwhelming the defenses and units to the point that I either run out of resources or they somehow sneak one drone in that wrecks havoc on the supply lines that are already packed with not enough space to add the turrets that can deal with the advanced units. Eventually, it really became a race to finish as fast as possible. Also, the staggered unlocks or limited resources on some maps were brutal.

Mindustry is much closer to the tower defense side of it.

Or maybe the RTS side.

There are even attack modes, where you build up an army to take on a fixed emplacement of enemy units.