WearOS is just a lot more taxing on the battery than what Garmin has because it does a lot more. The upside is that you get an entire ecosystem of 3rd party apps/services you can install.
Apple’s own apple watch doesn’t last much longer unless you basically disable everything.
Smart watches that work like a phone are inherently always going to have worse battery than smart watches that are only programmed to do a very narrow set of things.