As a Tottenham fan, I'm torn between the idea that this was always going to happen and I'm glad that Tottenham, by having a recent run of competency (until this season) has managed to get a seat at the table, and the obvious damage it does to the game. The European soccer model tying success in Europe to financial gains has always been problematic. On its surface, it is a pure meritocracy. Win games and you are rewarded by getting a cut of the UCL revenue. The problem is that it creates a system where the rich clubs remain rich since they use the extra European money to buy up the top players which keeps their team at the top, both in overall popularity (which leads to more revenue) and by allowing them to qualify for the UCL each year. Anyone who doesn't have the ability to muscle their way into the UCL each year is shit out of luck, and the result is a complete lack of parity in most domestic leagues.
The EPL is slightly different in that the domestic league is so popular/valuable that even the smaller clubs are able to spend some serious cash. The result has been a more competitive league compared to the other Big 5 leagues, both in the sense that they have a Big 6 (as opposed to 1-2 dominant teams) and that more of the mid-sized clubs (like Leicester and West Ham) can realistically compete for a top spot. The result has been that each year the league is almost guaranteed to have at least one of their marquee teams (lately Arsenal, who has an extremely large global following, perhaps only second to Man U) is missing out on the big tournament.
This is going to be kind of rambling, but here is what frustrates me the most about the ESL.
1. The complete lack of accountability for failure. Big clubs can continue to fail over and over again and continue to cash-in on the ESL and prevent other clubs from crashing the party. Recent struggles by Arsenal, Man U, the Milan clubs, etc. would bear almost no impact on the prestige of those clubs, outside of the fact that they will be in the bottom half of the table of the ESL.
2. The arbitrary nature of how the "elite" clubs were chosen. I'm not sure of the exact size of each fanbase, but it seems like a weird amalgamation of teams. From England, Tottenham is in but Everton is out. Okay, well Tottenham has been recently more competitive than Everton so that makes sense. Everton has historically been a more successful club than Tottenham, and more recently won the league than Tottenham, even if Tottenham has been more competitive in the last five years. However, you look at the Serie A teams, and the same standard doesn't apply. AC Milan has been a clown show for most of the past decade, while teams like Napoli and Atalanta have been sharp, successful units. But AC Milan gets into the ESL and not those better-run teams? So AC Milan's history as a top club counts, but Everton's does not?
3. The shutting out of successful clubs that have a long history of success in soccer. Ajax, Sevilla, Monaco, Shakhtar Donetsk, Porto, Benfica, PSV, etc. Clubs that have been very successful at the highest level getting shut out. Ajax making it to the semi-finals a few years ago was a truly magical moment and every neutral fan loved seeing an old giant awake.
4. If it does end up to killing the top teams from competing domestically, that will be an unbelievable tragedy. Imagine the Merseyside Derby not taking place twice a year, with a ton on the line? That is the real spirit of the game and it will be destroyed. Sure, the ESL teams will come up with their own rivalries over time, but it won't feel the same if Liverpool's biggest rival is Inter Milan and not their neighbors.