You're not really thinking about it as a "mac app", but rather "the service". You expect it to act like the service you use on other platforms with all the features you rely on.
If I'm using Spotify, I don't think "oh this doesn't use windows navigation component from winUI", I immediately know where the genre categories are because I've already used it on android or linux and expect it to be there. I know exactly how to add a song to my library, to shift around playlists, to manage folders, everything is as I learned it on [other platform].
Design development becomes this duplicated burden where every feature now has to go through the ringer twice (or more) to fit native components for their respective platforms. When you hit limitations on those native components, you're now having to make the decision to either hold back the feature entirely, or create fragile workarounds.
In an alternate timeline native components would have had far greater appeal, where people actually hate and boycott apps designed otherwise. But we don't. Even on iOS or mac, people regularly rely on apps that only vaguely interpret their native components. The situation is even worse on windows past 7, where the idea of a "windows app" is so jumbled there is nothing to "expect" from the experience - which is actually part of why I think these unified app designs have really taken off.