Upon the initial release of a film, these sites often host "Cam Rips" (recorded in a theater with a camera). These are never high quality. It often takes months for a genuine High Definition (HD) version to leak to these sites. While Deadpool 1 is older and likely has Blu-ray versions available on these platforms, the "High Quality" label is often a misnomer used to generate clicks.
isaidub is a notorious pirate site, so while the download is tempting, consider supporting the filmmakers if you can. That said, if you’re in a country where streaming Deadpool costs a kidney or the Blu-ray isn’t available, this rip does the job—and does it well. isaidub deadpool 1 high quality