I think all problems must be solved by that way that first step is to figure out what is real problem and then solve it. Current your solution is just changeing pillars more and more looking like houses so in one point you see that there is spam of houses but it is argueable is that house with functionality or just cool thing or something else. That solveing path leads into dead end and makes problem even more worse.
First step should be collecting ideas why players spamming with pillars not makeing pillars spam impossible.
Resource location problem:
Someone just build into valuable resource spawning area and resource is gone for everyone.
Pillars as resource protection solution:
most rare resources have spawn area protection by default. For example no one cant build anything in rich metal, crystal etc area.
tribes have special structure what dont affect spawning what tribe can put forr protect resources to avoid building. That structure is limited for example every tribe can build only 10.
Someone build something so close to my base as game allows and after that i cant build anything even exactly next to my base wall.
Lag and crash issues if too many are going to build lots of stuff too close to each other.
Pillars as territory protectionsolution:
make that foundations and pillars claim some area to us. That territory what they claim for us is depending on number of foundations what we own that area.
Pillars as protecting roadssolution:
makeing into game paths where players cant build anything.