It isn't worth your time to give free feedback to an employer as to why their actions/inactions motivate you to leave.
If your employer wants to FAFO and lose talent that's on them, if they want answers, just tell them eff you pay me – you completed your responsibilities and there's nothing you can say that will benefit you since you're leaving.
Exit interviews are just another exploitive effort by employers to make people do more work for them, often for cheap or free consulting often capitalizing on the employee's ill feelings, don't fall into that trap.