Caffeine is one of the nootropics that actually works, and has a measurable and proven impact. (Many, many others seem to be driven by placebo, anecdote, poor studies, or only useful for people with a specific deficiency.)

Most substances that do actually make a noticeable difference have some sort of drawback. That's just kind of how things go. With caffeine, some of the drawbacks are quickly building tolerance, addiction, anxiety, and sleep issues. Those don't effect everybody in the same way (for example, as long as I don't take caffeine after around 2:00 or 3:00, I don't notice any sleep issues). L-Theanine is effective for a lot of people in smoothing out a lot of the negatives (but I don't like it as much, because I prefer the higher stimulation).

So caffeine can be effective, but if you want to get the best mileage out of it, you should cycle it, and try not to use it every day.