Yeah, the role of Quint was iconic and was part of what made the original so good. But that being said, I think it was smart to not try to duplicate that character trope in 2. From what I can recall about 2 after all this time, it worked reasonably well because they struck a decent balance of taking some of the formula that worked from the original while still making the storyline different enough that it didn't just feel like a retread. I think trying to put in a Quint character would have taken them too far into retread territory.
Along similar lines, despite the uncanny coincidence of an abnormally large, predatory shark for those waters (or so it was believed at the time) exhibiting uncharacteristic behaviors TWICE, I think it was smart to not try to get into some bizarre explanation of "why"--like some offbeat scientific discovery that nuclear waste released off the coast of NY traveled by current to a previously unknown great white breeding ground not far from Amity, or something dumb like that. It was just perhaps the world's most amazing and unfortunate streak of bad luck for the Brody family, and they just left it at that (until pt. 3 anyway).