I’m also a slow gamer. Take HLTB as a rough estimate, then add ~15-20% over if it’s not absurdly bite sized like a tiny puzzle game and gas quests, exploration, narrative, etc.

HLTB is also a matter of averages, and the people who are likely to report are also a self-selected sample. Don’t beat yourself up for it; as long as you’re enjoying your time that’s what matters most.