This has not been my experience. No cpu issues, I can see time stamps on messages if I choose, I can search messages, if there are feature differences between mobile and desktop they are not features I am using, and between my Apple Watch, iPad, iPhone and Mac, all my messages are sync’d just fine.
To be honest, the apple ecosystem stuff and how well it works, for me, is one of the biggest benefits of Apple. I walk up to my computer and my watch unlocks it. I can take a call or respond to a message literally on whatever device I happen to be on. For me, I can put up with UI/UX quirks in features like system preferences that I use maybe one or twice a month.
Its the holistic experience that matters to me.