Precisely this. Your grass would be dead (little to no sunlight/"suffocated") and you'd (likely) have weeds & tree sprouts everywhere if you just left deciduous leaves as they fell. The best thing to do (IMO) is:

(1) Yes, not obsess over them (even if you do a perfect job, it's windy all winter and leftovers or your neighbor's leaves will eventually blow through - make peace with a few leaves out there, the place still looks great.)

(2) Do a decent job mulching most of them, it reduces erosion, feeds the grass, and avoids blocking the sunlight. Oh, and it's usually easier to do than raking/moving/collecting them all.