What I meant by not caring about the SQ, - is that many of their recordings were originally really bad SQ. Not talking about mastering with compression for radio....
We need to be careful with the term "louder." If it's actually "louder" than the upper treble, cymbals, vocal "s"s are sibilant and way to hissy, - IMO, - a better term is "hot to tape."
As opposed to compressed, - which is different, - in that the signal is "squished" so that there are no quiet parts, and no loud parts. This was done for radio, - so that there would be no dead air.
U2 have made some great music with some of the worst recording values ever. Sadly, ironically, one of the greatest producers, engineer, songwriter, and noise creator, Brian Eno was all over the wretched "Unforgettable Fire" recording. It is truly horrible. October, was also a horrible recording, - IMO.
I suspect that these bad U2 recordings cannot be fixed, as they came from the studio that way.
Remember, before a consumer gets a product in hand, - it is likely be 5 to 7 generations violated.... And, IMO, mastering should only refer to the process of cutting glass/metal/lacquer...