WotC has provided a full list of changes between the 2014 and 2024 versions of Dungeons & Dragons' Player's Handbook.
The changes include classes, backgrounds, species, spells, stat blocks, feats, equipment, rules, and new terminology.
Also included is a list of things from 2014 which are still usable in 2024, which includes 7 subclasses, 2 species, and 3 feats.
There's a separate list which details the changes to the D&D Beyond platform.