I remember that when many others and I said that the show was really repetitive in relation to other WDW shows, lacked imagination, had too many expositions, and made the same mistakes that Harmonious did (storywise), we kept being replied that the show was popular and well-received by audiences, just because these same people saw a few families with smiles on their faces. This was a failure in the making. Epcot should always have a mature and original show, not just a worse version of the great Happily Ever After...
You're reading too much in to the scores. Len uses a 5 point system which -- like any other scoring system -- has its advantages (it's simplicity) and disadvantages (lack of fine distinctions).
A 5 point system is like a 100 point system, but you tell people you can only choose: 20, 40, 60, 80, or 100. No 90s, no 70s, etc...
And so anything that is relatively good gets a score of mostly 4s (80s) or some 5s (100s). That means for all the good attractions, their scores will cluster in the range of 4.00 to 4.30.
If we were to take the scores that Len gives and inflate them to a 100 point system, it would be:
Show | 5 Point Score | 100 point score |
IllumiNations: RoE | 4.31 | 86.2 |
Luminous: tSoU | 4.18 | 83.6 |
Harmonious | 4.12 | 82.4 |
EPCOT Forever | 3.97 | 79.4 |
Everyone's favorite and gold standard, RoE, only gets an 86.2 on a inflated 100 point scale.
I'm sure if people were able to give it scores above 80 (4 on a 5 point scale) without committing to 100 (5 on a 5 point scale), it would score much higher.
The other indicator of popularity is whether people are staying in the park to see it over and over again, or, if it was a one and done.
For, me, EF and H.us were one and done. And insiders were telling of how Disney and the EPCOT restaurants were not happy that that was the case for a lot of people and the number of guests staying for the fireworks were fewer and fewer. But, they also have said that tSoU has turned that around.
And in the end, that extra crowd that buys merch and makes use of the restaurants and food kiosks is what counts for Disney... and is a sign of tSoU's greater popularity than H.us.