How to identify weak players at the table?

There is a saying: "if you can't spot a looser at the table within 15 minutes, you are the looser". What are your proven methods for spotting a weak player at the table, apart from a high VPIP ratio or betting non-standard bets (5bb). Feel free to share your experience.

For me, the easiest way to spot weaker players is to watch how they react when the situation suddenly changes.
A good player adjusts the plan a weak one just keeps calling because “they already put chips in.”

I also pay attention to timing tells:
instant calls in tough spots or snap-bets on scary boards usually mean they’re not thinking about ranges, just their own cards.

After a few hands you can clearly see who has a strategy and who’s just clicking buttons.

He only focuses on his own cards and fails to adjust his strategy based on the style of the other players or the community cards on the board