This question appears when you search for current (2024/2025) autocompletion issue in intellij without language specificity.

So for this actual and more generic issue: intellij ia autocompletion is super slow and kind of useless. This can be disabled in:

Settings > Editor > General > Code completion > Machine Leaning > Assisted Completion

Then, uncheck Sort completion suggestions based on machine learning

This should get things back to normal.