Fantasy vs. Science Fiction

that Arda is very, very well-developed, or that it is the highest quality fantasy.

Arda is "well-developed," and there doesn't seem to be anything "more well-developed." I didn't say it's the highest quality fantasy; unfortunately, I have no idea how to divide things into "high quality" and "low quality."
There's some kind of external criterion here.

There are many fantasy universes that surpass Arda in terms of development and interest.

Well, that's just your personal opinion. I don't think that Dark Elf "surpasses" Lord of the Rings, for example. However, it's not worse or better; it's just different.

By the way, these two elements together don't really coexist well:) there aren't many examples of good technofantasy.