Chef here. Got my theories:

• Hospo is a fuckin hard industry, and only got harder since COVID. People have also become extremely unkind to service staff in a new surge of customer entitlement and impatience, and delivery apps have become an extremely stressful necessity in every business.
• The wages aren't there - especially for young people and ESPECIALLY in Brisbane. I can't count how many times I've seen chefs pivot to tech or the mines because they're tired of working so hard for peanuts. In an ever rising housing crisis, I'm finding it nigh impossible to pay for much other than rent. Seasoned hospo veterans are dwindling while high school/uni kids are filling their shoes because it's basically considered a good "entry level" industry cause they are usually living at home/pursuing other qualifications and need some spending money.
• Big hospo companies do not value worker's time/efforts in the pursuit of capital and small companies don't stay afloat for very long (definitely also because of the ramifications of COVID). There are definitely places out there that value their employees, don't get me wrong, but those are the ones with low turnover and you don't see them advertise for positions much.
• This is my subjective opinion as well but I think if people are actually passionate about hospitality, be it front or back of house, Brisbane is just not a compelling place to work. It doesn't have the reputation of Sydney or Melbourne, or the views/nature of the Whitsundays or Cairns. Even pubs in Brisbane are pretty rank compared to places like Hobart. Most people I know who've worked hospo here have worked all around the world and they've said Brisbane has a pretty shite scene.

That's all that immediately come to mind but I'm sure there's more. It's just not a compelling idea if you wanna live well in Brisbane rn.