Is 500 LC questions good enough to pass a NG faang-level interview?

It's not about how many problems you do but how you do the problems. I run a program that trains people on their DS&A gaps, amongst other things, so I've seen hundreds of people progress from basic DS&A to a FAANG-level bar (i.e. passing a FAANG DS&A interview). The analogy that most resonates with people is this. The best and most experienced handy person can solve a lot of household problems with simple, well used tools in their tool belt. They have built up years of problem solving ability through practice and experience and know the right tool to fix the right thing. Doing 500 LC problems with little experience is like becoming a handy person by going to Home Depot and buying a $1000 set of fancy tools that you don't really need. You want to become the handy person that can hang a painting with a hammer and a nail, rather have like a $200 laser leveler, three different bolts because you aren't sure which is right for the painting's weight, a ladder because you want to drill the bolt on at the perfect angle, etc... You'll be a lot more efficient and successful with knowing how to use a simple set of tools properly.