Then be upset. Nowhere did I agree to reply to emails quickly, if at all. Your expectations, your feelings, your problem.
I am not personally upset if people don't get to my emails right away, because if I have anything actually urgent I'll get a Teams message out to the person who I know can handle it. (That does change a bit if the communication to to an external vendor in which case it's going to their support team who I do expect to respond promptly).
I stopped treating my inbox as an obligation and I reply at my own pace. I still give each email as much consideration as I can, but I no longer feel that it’s required. Some emails go unanswered.
I am slowly working on setting boundaries, especially in response to expectations that I did not opt into. It’s indeed a very contextual reply.