Agree with you when it comes to the big clubs. It's not something United or Barcelona fans are particularly going to bring up when talking about their club's history. Not now at least, suppose there's a chance should either face many years in the wilderness and not winning much of anything then a Europa League would become very exciting and a fantastic thing to cheer for again.
We're nowhere near at that stage and are unlikely to be. It would probably have to take some sort of financial collapse for us to ever get there as our monetary power means we should be looking to compete against the very best and as long as we have this kind of money the Europa League will always be viewed as a bit second-rate or an underachievement. It's just the way the game has gone. Pre-money UEFA Cups or Cup Winners' Cups are a bit different.
Would disagree on Sevilla to an extent, I certainly know what they did and think most keen followers of the game do. I'd imagine most who come to a site like this regularly do but If "most people" includes casual observers then possibly not. It didn't make them a fantastic superclub in my eyes and it's not going to but it was a great achievement for them and for their fans it must have been amazing. It put them more on the map than they previously were. If it was Real Madrid doing the same then no, definitely not, it wouldn't have done the same. I liked Fulham's and Middlesbrough's runs to the final of this competition in the past.