My point is that even though you say this will only replace the CL and all other competitions will stay the same, they won't will they. This effectively makes the chase for top 4 null and void as the six clubs normally scrambling to be in it won't need to bother as they'll have their position guaranteed. What does that mean? Well with a European place already guaranteed and say, for instance, we're too far behind in the Prem race, clubs will play second string teams to save their players for the ESL. You could argue that this happens now to a certain extent but the difference is that currently, whilst you might rest a few for an important midweek game, you still take the league match seriously to make sure you qualify for the CL next season. All of that would be gone. We would be permanently in European competition. You'll be surprised how quickly this will get boring.
The fun is had achieving it, not having it handed to us on a plate.