Every job I ever had in HK required Mandarin and Cantonese, too. Do I speak them in a business sense, no. I had to do some work on the mainland before, which is a shit show. But the rest of Asia is pretty legit and fun to work in, and English is sufficient.
HK is weird about job postings, here's a sample of what a typical job ad would say.
Looking for experienced professional with Law degree, medical doctorate degree, with 20 years experience in mainland China, Asia, HK, Europe and USA. The applicant must be born and raised overseas, only HK permanent residents shall apply, no visa sponsorship. Further the applicant must be willing to travel and work days nights weekends and holidays. The applicant must speak native English, native Mandarin, native Cantonese, native French, native German, and native Japanese. Provide your full CV, all work experience, work certificates and education certificates including your K1 and P1 records.
Apply now, will only respond if your salary expectation is lower than that of my domestic helper.
Yeah I'm exaggerating, but so are most of the job posts out there. Language is rarely a reason for not getting an interview, provided that you speak English is the bare minimum usually. Although many people get hired only speaking Canto with poor English too.