what is the best way for me to get to HKIA for connecting flight from Guangzhou Airport?

Hi, 1, take Airport line 6 and get off at tianhe mansion: 20 yuan. one hour.
2, Take a taxi to guangzhou east railway station： 8yuan, 5-8 minutes
3, take the train to Hong Kong kowloon: 44 yuan for soft seat, 2 hours.
4, take the free bus at the Kowloon station to the Kwoloon Airport Railway Station: free, no more than 10 minutes
5, Take the airport bus at Kwoloon Airport Railway Station: 20 MINUTES, 90hkd.
The total time cost is about 4 hours.

I am wondering why not fly to shenzhen airport from haikou and then change to hong kong from there. It is quite convinient from shenzhen airport and Hong kong airport. There are shenzhen-hong kong airport link operated in shenzhen airport . Very convinient. See this for shenzhen-hong kong airport link if you would like to change from shenzhen https://www.travelchinaguide.com/cityguides/guangdong/shenzhen/transportation/