Turkish Airlines Seat Assignment and Check-In Issue

Because we trusted the THY brand, my boyfriend and I purchased our tickets through Turkish Airlines even though we knew we would be flying with AirAlbania to Albania. On our return trip, we chose THY again for our Istanbul to Antalya flight. We were unable to check in via mobile. When we arrived early at the airport and tried to use the kiosks for self-check-in, it indicated that no seats were available and we needed to go to the counter. The gentleman at the counter looked at the screen for a long time and made a call. When we asked if there was a problem, he said the plane was full, which surprised us. Later, they told us that we could sit separately in different seats. Since we didn't want to lose our tickets, we had to accept. When we boarded the plane, we saw many THY staff members seated. I went to my seat, but someone from the staff was sitting there and, despite knowing it was my seat, they didn't say anything out of courtesy, so I had to sit elsewhere. Not only did I not sit next to my friend, but I also couldn't sit in my assigned seat (I asked why there were so many staff members, and I learned they were traveling for assignments). I saw other passengers who couldn't find seats being allowed to sit in Business class. Due to these issues, I am hesitant to use THY again. I don't want to experience the same problems. Our trust has been shaken.