Fallout has been quite literally hung, drawn and quartered and then crudely stiched back together using mostly parts other games. A mistreated series indeed; lauded for what it was and given so much of the as-if kind of respect that never, after 1998, has there been a proper sequel. For a history in a nutshell... First there was a proper sequel to Fallout, a game that did miss the mark on certain aspects but retained the core, then the series went to being a tactical combat game, then a copypaste of a completely unrelated fantasy action game, then a copypaste of another completely unrelated fantasy action adventure. So here we are today. A cult series forcefully mutated into something completely different from what gave it that status.
What do I miss from the old games? Everything. The mood, the tone, the structure, the gameplay and mechanical intrigue, the art style, the music, the wealth of roleplaying opportunities that the game actually provides and supports, the interplay of those aspects that created the experience still like no other. Almost none of that is left anymore -- the latest game did an admirable job at bringing back that narrative flare but didn't manage to (nor want or could) bring back the gameplay ideals. The series now strives for a different experience for a fanbase of a different mindset, than it used to. What is really left for the series, in relation to what I miss, is to keep fingers crossed that at least some the old magic is brought back in some manner that fits with the emperors new clothes.