I reply all to all work related emails because people will add someone who needs to be aware of what’s happening and I may not realize this is important to them. If they don’t want to be on the email they can ask me personally and I’ll take them off the chain.
I never reply all (or at all) to company update posts (e.g. new hires/promotions/other bs). If you want to congratulate them do it privately. The whole company doesn’t care.