Elves who live hundreds of years are nonsensical to me because of how overpowered they should be but aren’t. Like an Elf who’s been training for hundreds of years but loses or only matches up to someone who’s only been training for few does not make sense to me. I could understand if long living Elves weren’t talented (something I plan for my story) but when they’re portrayed as geniuses it makes even less sense. Any thoughts?
It's actually easy to justify. Due to their long lives, the elves feel no sense of urgency. This means they just live life slower and spend more time playing and messing about. Maybe the reason why an elf who has trained for decades can be matched by a human who has trained for years is because the human has trained 6 days a week for the entirety of those years of training, while the elf has only trained 1 day a week and maybe hasn't even kept that light schedule consistent.
So, yes, the elf lives longer. However, the human is living 6X faster and focusing their efforts on a single subject, allowing them to match the elves in that one subject they focus on.
You see this difference in life approaches among different people in the real world. Imagine just how much more pronounced the effect would get if you effectively remove the urgency of getting old and having a tight time limit to get things done.
Basically, elves are just lazy.