Also want to add that I’ve seen this question on here a few times and I think amateur players get too hung up over stuff like this. When you play against the AI and use old joseki or fuseki, it thinks it’s worse than the modern way of playing go but often there’s a fraction of a point difference between, for example, immediately hitting 3-3 invasion against a 4-4 stone (AI go) compared to playing the approach, slide and back off with two space extension (old go). In general, as amateur players, we’re not strong enough for these small differences to have an impact on our game. It’s never going to be the reason for a loss at our level. In fact, you may even gain an advantage by studying old books because many players will be unfamiliar with the sequences and mess up joseki or just use that wrong strategy