There have been multiple tests where people get a proper VO2 test done on the treadmill etc and it’s pretty accurate. My Garmin watch says 49 and my Apple Watch says 45.4. I think the Apple Watch is probably more accurate as I’ve worn it for years whereas the Garmin is only a month old. The more runs you do, the more accurate it will be. Whilst I understand that it must be discouraging to be in that range, if you put the effort it, the only way is up :)