In my opinion, though, a EPL/FA/EUFA treble is more valuable than a La Liga/Copa del Rey/UEFA treble.
Yeah, the EPL may not be the best league in Europe (certainly behind Bundesliga and La Liga at the very least), it may very well be the deepest, with teams way down the ladder being competitive against the top teams.
Much harder to win multiple trophies there and still manage a successful EUFA campaign, as the domestic titles are just harder to come by week in and week out, and they can’t cruise a bit and focus on the UEFA games as much.