Well…

It all depends on what kind of decisions you are saying the groom’s parents are being left out of. And what the groom needs to take a stand about.
I think you have a more specific question, or something that you personally may be dealing with?
Should the groom’s parents be asked how many guests are absolutely necessary? Yes.
Where the reception will be? No.
What will the menu will be? Colors of linens? Open bar or not? No.
Do you see what I mean? These are not something the bride’s parents need to consult the groom’s parents about. They will confer with the bride and groom, but since they are not the hosts, the groom’s parents are yes, left out.
I will say this again. Pinterest has really raised the bar of bride expectations. Unless they or the groom’s parents are paying for all of it, they may need to dial back those expectations to reality.