To add another data point, I also moved on from Postman a while ago. Similarly to several commentors here I had found it to have become bloated, slow and buggy imho. In my particular use case, I found the urlencoding when using oauth1 to be pretty buggy. It would sometimes not work on certain headers it generated.
My team ended up moving to Paw but that has been a bit problematic since it only supports osx, so some team members are also using insomnia which doesn't seem to be much better in my opinion.
I recently found httpyac[1]. It's a cli and file based http client similar to the IntelliJ HTTP client, but has plugins, hooks and allows scripting through javascript blocks. It seems to have everything I need but I haven't used it much yet. It also already supports gRPC.
One of the issues I found with http clients I looked into is that they often don't provide enough functionality to hook into the request process. Either before or after a request is executed to add to the headers or parameters of the request or getting the results of the request. Postman did provide some of that but that's one area I wanted more from any client I looked at. I could of course simply wrap curl in a script but at that point, I will be maintaining my own jerryrigged version of an http client for my team.
It's built on a plugin architecture, does gRPC, GraphQL, JDBC, Ws, et.al. Other plugins allow sharing of workspaces to various services. Written in Java/JavaFX, brew or chocolatey install.