Morty - Here's my take on your tree leaf situation, fwiw...

1) Burning the leaves off of live trees will injure the trees, and likely will kill them, maybe not right away, but eventually. That will put you in a situation where they either
must be cut down, or left to decay, shed limbs, and eventually fall.

2) If you cut and remove them you will be removing a point source of pond detritus. I'm sure these aren't the only trees in the neighborhood, and the wind blows all winter, so the
major reduction in detritus that you're hoping for may not pan out as expected.

3) If you're not comfortable cutting them yourself - don't. Hire a pro. Felling trees is dangerous, especially for people who are not experienced at doing it.
There is a lot of energy stored in a standing tree. You don't want that energy transferred into your body when a tree falls on you, or kicks out and launches you halfway across the pond.

So it comes down to weighing the pros/cons of removing them, and then deciding if the pros (reduced organics load, slower water loss in hot weather, etc.) outweigh the cons (removal cost).