To play the devils advocate, being able to memorize patterns and recognize which patterns apply to a given problem is extremely valuable. Tons of software dev is knowing the subset of algorithms, data structures, and architecture that apply to a similar problem and being able to adapt it.
It's funny you mention that.
That's literally what CS teaches you too. Which is what "leetcode" questions are: fundamental CS problems that you'd learn about in a computer science curriculum.
It's called "reducing" one problem to another. We had an entire semester's mandatory class spend a lot of time on reducing problems. Like figuring out how you can solve a new type of question/problem with an algorithm or two that you already know from before.
Like showing that "this is just bin packing". And there are algorithms for that, which "suck" in the CS kind of sense but there are real world algorithms that are "good enough" to be usable to get shit done.
Or showing that something "doesn't work, period" by showing that it can be reduced to the halting problem (assuming that nobody has solved that yet - oh and good luck btw. if you want to try ;) )
I did quite a bit of competitive programming in school, and pretty much all the world-class competitive problems are reduced to well-known algorithms. It's quite hard to come up with something new (not proven to be unsolvable for its constraints). I believe problem setters just try to disguise a known algorithm as much as possible.
Then comes the ability/memorization to actually code it, e.g. if I knew it needs coding red-black tree I wouldn't even start.