I don't think the rules have changed in spirit (especially in 5e) but the mindset has. Basic D&D was very ridig if you followed the rules (like a video game, with codified turns, see "Sequence of play" in B/X https://i.4pcdn.org/tg/1509982170193.pdf). AD&D already had a rule for everything. But the mindset was DM were loosely following the rules apart from character tables and were making their own house rules for everything. Everybody had a different understanding, sometimes were young, and there was no internet to check if it was correct, as long as it was fun to play.