"Here’s a more polished and balanced version that maintains your disappointment while acknowledging the staff’s prompt response:
Writing
I have stayed at this hotel several times in the past, but on this occasion I was very disappointed for a number of reasons. In particular, the standard of cleanliness in the room was far below what I would have expected. However, when I brought this to the attention of reception, they acted immediately to address the issue, which I appreciated.
Unfortunately, this experience, along with other concerns, has left me feeling reluctant to return to the hotel. I appreciate that things can sometimes go wrong, and I am willing to remain open-minded and give the hotel another chance in the future. However, I hope that greater attention will be paid to maintaining the standards that returning guests have come to expect."