No, it's a mixture of airline staffing and airport staffing in general. Some of the worst hit appear to be holiday charter airlines such as TUI, which would not really be considered a budget airline.
Not to forget BA have cancelled 100s if not 1000s of flights and they are supposed to be a flag carrier. Much of the cancellations can be laid at the feet of the companies treating their staff like **** and in the case of BA, have put a lot of the staff on new contracts on reduced terms during the pandemic. After the pandemic, the jobs market became a workers market so a lot of them moved on to other jobs as they could afford to be more selective and who can blame them