I don't think that's as big a factor as made out. Ziyech, Pulisic, Werner and Havertz were convinced to come here when CL football was still far from secure (3 of which from teams all but assured of CL football) while Jorginho, Kovacic, Luiz and Kante all came here from CL clubs when we didn't have it, a top class manager like Conte came here with no CL football, flavour of the month at the time Sarri gave up CL to come here.
If we look across to our competitive rivals Arsenal managed to nab Auba and Pepe without CL (as much as he's been a disappointment he was one of the hottest properties in that market), United got Pogba, Di Maria and Ibra, Liverpool got Suarez, City got Silva and Tevez, Bayern got Ribery, Juve got Pirlo etc.
I mean if Leicester and/or WHU with all due respect to them make it over us would they beat us to signing's? It would take a very short sighted player to make a decision based on what could end up being six games.
The players that do tend to make CL footy a deal breaker are the one's who tend to end up in Spain. The likes of an Mbappe/Haaland is a closed market for us even if we win the CL.
I think a combination of our club reputation (all the active young/prime players grew up seeing nothing but Chelsea success) plus the good package we offer will convince many a player to overlook the odd season out of it.
I think we're in an unusual position where we're big and rich enough a club to be a serious contender for all but a very few players, and therefore the promise of CL football becomes very important. We've been one of the big European clubs in recent memory, and that has real value for the players who grew up during that period. But they won't necessarily sign on without the CL guarantee.
Maybe I'm wrong, and maybe its not as crucial as I think, but we'll see I guess. I really want us to get Haaland and I don't think he's out of reach at all given Madrids situation.