They can't be processed quickly because naturally their lawyers (paid for by you and me, no less) drag out appeals for as long as possible.
Whilst I wouldn't be in favour of sending a genuine political refugee from a nasty brutal totalitarian state such as (say) China back whence they came, Blind Freddy knows that 99% of the 'refugees' in Hong Kong are economic migrants trying it on.
It's a horrendously messy kettle of fish and once you start working through all the permutations of implications for taking this or that approach to solving the problem, one quickly gets a headache. Many of the things which need to be done to discourage illegal immigration could easily establish precedents for mistreating legitimate Hong Kong Residents.
But there are perhaps creative ways of encouraging people to go back whence they came: e.g. determinging after careful study that they would be safer out of the general community and building them a nice 4-star recreation centre camp in the middle of the LOHAS landfill.