Good Point!
It is true that I thought that before the release of FS2024, like “ok, it is much more detailed and better resembles the real world like a digital twin, so it is fully acceptable that it shows lower FPS”.
But looking at the sim now: Yes there are more details when flying low. But from higher altitudes it looks quite the same as FS2024. In many parts the digital world consists of exactly the same building types as 2020. And I found many parts of the world I have been to in RL now looking less realistic. E.g. parts of the earth covered by huge rain forest trees, where in reality are some bushes and agriculture. Both the house I grew up and also the appartment building I live in now have been merged with other buildings and now look unrecognizable - that was not the case with FS2020.
So the new world data in some parts has not improved, it got worse. In general it is not more detailed or only in a few aspects.
So if two sims look more or less the same from mid altitude - the newer one not better in many aspects - then it would make sense to expect about similar performance.
BUT! I have always compared FS2020 at very high settings to FS2024 at low settings. And still FPS are much worse with FS2024.
Means, the scalability graphics wise is not there - the sim seems broken performance wise. Would be interesting to learn what went wrong in the making of FS2024.