So you mean from all those who apply only a small number would get through, and that would be through the lottery for how many applicants? Do you know how many people get through the PGP lottery and get selected, versus the large pool of applicants who apply!
Yes, that's now it works. Around 10% of total applicants were selected last time.
But as others have said, you won't qualify to enter the lottery for several years yet if you don't meet the income requirements for 2020. Earliest you would qualify to submit an entry into the lottery is 2024 (this assumes you make enough income in 2021, 2022, and 2023).
If you don't want to wait this long for your parents to have PR, then the other option is for them to qualify to immigrate on their own through an economic immigration stream like Express Entry or PNP based on their own work experience, level of education, language abilities, age, etc.