Yes, it's working but am I missing out on some must-have features or will I get slower responses as a result?

"Must-have" is relative. Net::Amazon contains all the features that were "must-have" back in 2009. Only if the scope of "must-have" has changed (and that depends on your use case) there is a need for improvement.

was just wondering what others use because I'm just starting with this and, to my surprise, I couldn't find anything more recent at all.

I found Net::Amazon and XML::Amazon quite convenient, and only implemented my own becase eventually I want to use non-blocking requests with Mojo::UserAgent for nice integration into the Mojo runloop.

That said it was a lot of work, and I wouldn't recommend it - for most use cases it's much easier to extend the existing modules (submit patches to the module author) than to roll your own.