Turkish Airlines Rescheduled My Flight Reservation and This Affected My Travel Plans

I booked a flight for three people on January 11, 2024, via the THY online site for the Istanbul-Antalya route scheduled for May 26 at 11:10. As we usually travel by car for our vacations, I decided to book a flight this year because my spouse and young child really wanted to fly. Up until April 2, 2024, the flight time changed 3-4 times due to operational reasons. This has become quite frustrating, and the latest given time is 17:30, with other times being fully booked. Traveling at this time means wasting a day's vacation cost.
For the return flight, I booked a reservation on February 12, 2024, for the June 1 flight at 11:55. This flight's time has also changed 2-3 times, and the latest time given is 07:40, with most other times being fully booked as well.
By trusting THY for our vacation plans, we have been let down. Flight disruptions can happen once or twice, but not to this extent. If a suitable time is not provided or an additional flight is not added, we will be forced to cancel our tickets.