Any fan from any team would be dumb if they want a rival team to do good internationally just so the reputation of the league gets better.
I doubt United fans are happy that Liverpool and City are doing great in Europe, while United doesn't challenge for any title.
I'm pretty sure you would rather have a situation like in the 90s, where EPL was behind Italy, Spain, Germany, and France in UEFA coefficient (because Leeds, Newcastle, and Blackburn were constantly getting spanked in Europe), but United was winning most of domestical trophies.
At the end of the day, nobody in real life cares about the reputation of a league, it's mostly an internet banter.