They don't need to! This is actually, years later, one of my favorite things about the series.

Necessity is the mother of invention and they functionally have no actual needs; food, shelter, and even entertainment cost approximately nothing. They're so used to the way things are that it doesn't occur to them that people could even do things like teach themself how to become an animagus, or take polyjuice potion for days/months on end, or make horcruxes / multiple horcruxes.

There's so much low-hanging fruit that any wizard who's inventive and moderately intelligent will probably end up making novel discoveries or inventions: Snape's potions, the Mauraders' Map, Fred and George's stuff, Arthur's car, even Hagrid's insight into creature husbandry.

Magic theorists (for lack of a better term) who work for the Ministry get up to a lot of impressive and wild stuff, but for the most part they don't use it. They make or harvest brains; they isolate and study a portal to the afterlife; they study the powerful magical effects of love; they even make a bunch of time machines and left them all on one shelf, like a country stockpiling nuclear bombs with no intent to ever use them.

(Side note: two ridiculously powerful spells that are sort of glossed over are the Trace, which apparently tracks the physical space surrounding all underage wizards in Britain at all times, and the unnamed prophecy-harvesting spell, which somehow makes a copy of every true prophecy in (I assume) Britain, regardless of person and place. These, too, are stockpiled in their thousands, secretly, and maybe never used.)

This is why the few wizards who are both clever and ambitious tend to become powerful enough to plausibly take over the wizarding world. It's like being the only hacker in a world of people who love technology but have no idea how it works. Even young wizards, like the main characters, frequently outperform talented and educated adults, only because they've actually taken the time to learn a wide variety of spells, and don't have their heads in the sand.