I can understand the frustration about fighting it.
You just park your arty right outside your base and protect it with mines zwhere bunkers and what not.
Then comes the second frustration
I need to pick a commander especially to counter arty spamming, which just leads to more frustration.
There is no other way to deal with arty than becoming an arty spammer yourself
I'm not sure there was a question in this? Unfortunately yes, one needs to pick arty & call-in abilities to deal with SPG/fixed gun spam unless they skip enough defences for a dive to be feasible. That or break their back in the field and overrun. Fixed guns can't retreat at least.