Aeon's End and Deep Rock Galactic immediately come to mind here. Both are great games, but the instructions are terrible.

AE somehow manages to extend fairly simple rules into very long paragraphs, making it seem way more complicated than it is in practice.

DRG lacks icons for most effects, which decreases readability. It's also sorted in a way I can never look something up quickly without reading entire pages to find the relevant paragraph, with some explanations being in the scenario book instead to make it worse.