Yet there is also SO MUCH in 1E that is short-sighted, contradictory, readily used in a mean-spirited way and far clunkier and a block to smoother play and fun. Because it is a product of its time - an edition that was created before "RPG design" was a PROFESSION and everything that was done with it was new and different that all later editions would build on - it MUST be house-ruled in order to address these issues. However, that was always what DM's were EXPECTED to do anyway. No "professional" game designer sitting anywhere that isn't MY TABLE really knows precisely what I need and want from D&D as the DM, much less what 4, 6, 10 players at my table all individually want and need. Those designers can only GUESS and aim their game at one particular chunk of demographics, and they can be right most of the time but rarely, so rarely, are they going to have got it just right for everyone at any given table.
Despite all its flaws, 1E AD&D is equally worthy, if not more worthy than 5E. It's more accommodating of customization than 5E could hope to be, even though that accommodation is effectively mandatory for every game.