It's not meaningless. You just have have to reset the scale based on the platform.

On Amazon, for instance, you have to ignore the first 4 stars. So it's:

Under 4 stars: total garbage

4.1 = 1 : a little better garbage

4.5 = 5 : About average

4.9 = 9 : Amazing

My wife and I have a rule: Books have to have at least 4.6 on Amazon and 4.2 on GoodReads (which is a harsher platform).

The Amazon scale above (ignore the first 4 stars) also works for Uber Drivers. An Uber with a 4.1 score is a danger to life and limb.