Seconded on the imposter syndrome point. I definitely have days in my life when my internal narrative sounds just like your post, but if I take a step back I'm much further along than at those low points.

Another issue is that it's entirely possible that your current role doesn't challenge you to learn or retain CS concepts nor deeper aspects of the practical tools you use. Many jobs can be done very well using the same shallow toolkit repeatedly. If that's the case, it's not really a question of your ability, but maybe you can start actively looking for projects to force yourself to start learning more.