Pretentious is such a lazy trope to be levelled at an artist. Blur absolutely are not pretentious in any way. They're moderately experimental, but they're hardly some high falluting avante garde band who refuse to play anything but the most impossible to play jazz chords
But lets be honest here, the Gallagher brothers are as thick as a boxing day turd, whereas all the members of Blur are moderately intelligent. That's nothing to do with class, it's to do with intellect. So it's a pretty fair comment about their lyric writing. That's not to say Blur haven't had the odd terrible lyric, they have.
If they were clever I'd happily big that up, but the music they wrote was pretty simplistic. Chord progressions were really bog standard, bass lines were largely playing the root note, the lead parts were good but almost exclusively pentatonic based, there was no use of interesting modes, many of the songs were in the major key (which to me helps with keeping upbeat and popular, but lowers interest), extended chords were scarce, they didn't really play with tension in songs. It's not pretentious to play with those things in your songwriting it's just learning your craft properly. Oasis did the basics well, and did it with attitude, but couldn't be bothered to improve themselves. They and were effectively the 90s equivalent of a boy band.....a lad band, living off tales of bad behaviour and sound bites.
They were an important band still, and you can't help but sing along, in the way that you can't help popping into a kebab shop after 8 beers, it tastes great in the moment, but it's not a good pub meal, or a nice restaurant.