I have hit a few barriers and the hardest is always the current one of course. However, I will say that I think the challenge becomes different when you get to around 20 seconds.
Above 20 seconds, most improvement is made by gaining competence, not speed. You get comfortable with the cube, learn your alg sets, learn to be efficient, and learn to recognize cases fairly quickly without hunting all over the cube. You make big improvements by pausing much less and making fewer turns, so you don't really need to turn that fast. Turning speed improves naturally with practice anyway, but you don't really need to push it because you make your gains in other ways.
At around 20 seconds, you are already competent. There are no longer such big wins to be made from improving efficiency. Maybe your recognition still has room for improvement, but the challenge shifts towards starting your recognition before you finished your last moves - lookahead - which is a more difficult challenge. Above all, you need to start turning faster, and that means not only pushing yourself beyond your comfortable speed but doing so while keeping composure, so as not to lock up or fumble the cube.
Maybe this comes at different stages for different people - for me it was ~20, but for you it might be ~25 or ~15 - but in my view it's the transition from learning to solve well to learning to solve fast that starts to present a more difficult type of barrier.