The details aren't really fleshed out scientifically, I will certainly grant you that. However, I think just the very concept of a drug/medicine/some sort of thing that can make you very smart is very relevant to real life. We are approaching breakthroughs in gene editing, brain-computer interfaces, and simulated people (AIs) that will lead to a scenario in some ways similar to Limitless. Sudden leaps in human intelligence will happen. I find Limitless to be a fairly interesting exploration of "What would I do if I suddenly could make myself a lot smarter?".

One of the main traits of good Sci-Fi in my opinion is that it leaves you with questions like these to ponder.