> there wasn't a concept of clean code but to write code as simply as possible

Sounds good "on paper" - in fact, is tautologically true - but it's hard to find two people who agree on the definition of "simple". You say "not having thousands of classes with indirection", and I've definitely seen that over-design of class hierarchies create an untouchable mess, but I've seen designs in the other direction (one giant main routine with duplicated code instead of reusing code) that were defended as "simple".