People pretty universally say the 7th is crap. I think the reason is only the last movement.
The first four movements are great. They are quite not as great as the 5th or 6th, which seems to say what they say better. In fact, each of the first three movements seems to be quite close to the corresponding movement in the 6th symphony, and to be outdone by it. But the middle movements are still all wonderful, and the 4th movement has a delightful urbane wistfulness about it, much more human-scaled than the Adagietto of the 5th. (It is after all meant to be scene-painting a night stroll around Vienna.)
It falls down in the last movement. Exegetes say that it’s deliberately meant to be bathetic, that Mahler is poking fun at the carefree style of the Strausses, just as Shakespeare made the problem comedies problematic, and Mahler himself made the finale of the 5th a study in anticlimax.
I buy it for the 5th. I don’t buy it for the 7th. It does sound to me like someone who’s trying to have a happy ending and failing; it does not sound to me like someone who’s doing that on purpose, to make a larger point.