Enough has changed that a lot of confidently repeated advice is now simply wrong. Here is the short version of what moved.
Captions became searchable text
Instagram search now returns results based on caption content, not only tags and handles. This is the single biggest change, and it means the words you write are competing directly with the tags you choose.
Speech and on-screen text became signals
Short-form platforms transcribe audio and read text in frames. A video that never says its subject out loud is harder to classify than one that does, independent of its caption.
Recommendation overtook the follow graph
What people see is now decided mostly by predicted interest rather than by who they follow. This is why follower count correlates so much more loosely with reach than it used to, in both directions.
Search intent arrived on social
Users increasingly open social apps with a specific question rather than to browse. That rewards content that answers things and punishes content that only performs.
What this made obsolete
Thirty-tag blocks. Universal posting-time charts. Follower count as the headline metric. Optimising the caption purely for personality. Treating hashtags as a reach lever rather than a classification signal.
What survived
Being specific. Being consistent. Making something people want to send to a friend. Those were true before any of this and remain the whole game.