I think it's less that gamers have decided it's the "endgame" and more that current gen games at good framerates at 4k require significantly more money than 1440p does, and at least to my eyes just running at native 1440p on a 1440p monitor looks much better than running an internal resolution of 1440p upscaled to 4k, even with DLSS/FSR - so just upgrading piecemeal isn't really a desirable option.

Most people don't have enough disposable income to make spending that extra amount a reasonable tradeoff (and continuing to spend on upgrades to keep up with their monitor on new games).