That is true.
But having a GB that reduces your defences kinda makes St basil’s, deal and Terracotta a bit redundant. A 20% reduction of a 200% defence is higher than what a level 10 defence boost of all of these GBs as a level 10 only gives a 30% defence boost for st basil and deal castle, while TA level 10 gives you 20%.
Also those who choose to put in WFs or ritual flames to beef up their defences are using valuable real estate in their city to do so. Therefore, I don’t think anyone should be penalised for choosing to have a strong defence boost as it is already costing them a lot of FPS and real estate to do so.