Phil,
You are a little bit of a music snob.

That doesn't make the songs, or artists (Led Zepplin) that you don't like, bad. It just means they are not to YOUR personal tastes, which are more narrow than some, that's all.
Songs can also get old from overplay. "Time in a Bottle" is a really good song, but it is the butt of endless jokes, and was sung all the time, everywhere, by everybody. That doesn't make the song bad.
Jimmy Webb is a wonderful song writer. Witchita Lineman is one of my favorite songs. His lyrics are often metaphorical and usually very good, but my Lord, it is the melodies and grand arrangements that are to die for. Witchita Lineman just carries you over huge sweeping landscapes. Brings you on a journey. While I haven't posted any of them, I LOVE writing what I call "flying music" or melodies that make you feel like you are soaring and flying. And Webb is brilliant at this.
Some of his hits:
Mac Arthur Park
Up, Up and Away
By the Time I Get to Phoenix
Wichita Lineman
Galveston
In any event, Mac Arthur Park was written around the 60's culture, of hippies and drug trips, etc... Webb was going for surrealism matching that, which is why ideas kind of flow one into the other. Mac Arthur Park in fact, too, was part of the imagery of the song, because in that time, it was a hippie hang out, where people practiced a free lifestyle, and that park was a kind of escape from the city buildings which surround it everywhere else.
Clearly it is a very good song, or it would not have been covered more than 50 times to date, including having it top the charts several times, in different genres and by different artists.
Like much of Webb's writing, it is the musical progressions and arrangements and melodies, that for me, are the more brilliant and moving parts of the songs. The lyrics could be changed on some of these songs, and they would have still been hits.
The music and melodies, are just breathtaking, on many of his songs.
.