Complex sentence: It is therefore more difficult to create a definitive list of Wainwright's outlying fells, and they are usually excluded from the list of Wainwrights, but many walkers still bag them.
Split into simpler sentences: It is therefore more difficult to create a definitive list of Wainwright's outlying fells. They are usually excluded from the list of Wainwrights, but many walkers still bag them.