I remember some reviews of this song when the single was released late 1965, and they mentioned the unlistenable lyrics. Because I'm from Holland (and my English is not that good), I can imagine what the reviewer's point of criticism was, but how was it really for the (young) fans from England and US? Were these lyrics too fast?
I think the lyrics are pretty clear for a Rolling Stones song. In America, we don't use the word "windscreen" so that might have been confusing.
Frankly, until I listened to this video, I had never heard Get Off My Cloud in stereo, always in a muddied mono . . never heard the hand-clapping at the beginning. I originally thought they Brian was playing a sitar during the song, but of course it is just a guitar with a sitar sort of sound.
In New Musical Express (oct 29, 1965) there is a story about Keith Richards hitting back on David Jacobs' criticism. On Juke Box Jury Davids said he couldn't hear the lyrics of Get Off Of My Cloud. Keith's reaction: "Perhaps he's a bit deaf". NME's own review is positive about the tune, but also mentions the lyrics: "(...) And again, it's difficult to get the gist of what Mick is singing. But who cares? It's the atmosphere that counts - and that's sensational!"