If you press "Enter" it just pastes in the autocomplete, if you press "Tab" it replaces it. I would guess you are always pressing "Tab", so try "Enter" and see if you like how that works.
Full Documentation from JetBrains
Here's the TLDR;
- Use Enter to insert the selected string at the insertion point.
- Use Tab to replace the string next to the caret with the selected one.
- Use Ctrl+Shift+Enter to make the current code construct syntactically correct (balance parentheses, add missing braces and semicolons, etc.)