Which is why I've been sorting out the leafmould bins for one of my clients. She has a fabulous big woodland garden, full of lovely mature natives like beech, oak and whitebeams (one of the loveliest trees if you have a chalky soil - it has silver undersides to its leaves). Unfortunately, though she has two massive leafmould bays, they were full of roots and half falling down, so they took a lot of work to get functioning again!
I'm there now though, after a couple of sessions of digging out a mixture of nettle and tree roots and sorting out the rotted stuff - some many years old - from the new leaves which had been dumped on top. Now I have two bays, about 10ft x 10ft (I told you it was a big garden) made of posts driven into the ground with green wire chainlink fencing round it. You need plenty of air in a leafmould bin to make good mould, so things like compost bins, with more solid sides, don't work: chainlink fences are ideal and last for years, though you have to have strong uprights which are well driven into the ground as the weight of the leaves can be enormous.
Now I have lots of lovely old leafmould to spread as a mulch on her borders. It makes a great autumn mulch as it's low in nutrients so won't spur plants on to put out unseasonally tender growth, and it still adds plenty of organic matter to the soil (desperately needed on her thin chalk). One of the many good reasons to have a garden in the woods!