I think this is fairly common at many companies, especially smaller ones where most employers, developers included, must juggle many balls at the same time. Only in larger developer teams and/or longer term projects can you really dig consistently deeper into a specific subject or area.
However, this situation has its good sides too: it exposes you to lots of different tools and technologies, widening your experience and skill set. This teaches you to pick up new subjects easier and faster, which may give you a distinct advantage in the future when looking for a new job. So embrace these opportunities and strive to get the most out of them.
Digging deeper into a technology / tool and becoming an expert of it (above what is explicitly required to do your current job) is not specifically supported by most companies, because - from the short sighted economical point of view - they may not see any direct benefit of it, OTOH it may increase the risk of you leaving them for a better job. (Of course, the rare top-level companies know very well that actively supporting you to increase your competence will bring them better, higher quality, more efficient solutions in the future, and increase your job satisfaction too, making it more likely that you stay with them - this is what makes them top level, after all :-)
However, alas, most companies are not quite there. Note though that this depends on you much more than on your employer. If you make a conscious effort to push yourself further in one or more favourite areas, allocating a part of your free time to experiment, study, and/or work on open source / pet projects, you are on your way to become an expert. You may also want to raise the subject with your manager, to discuss how the company may be able to support your education efforts better. In the best case, they may pick you more interesting / challenging projects, send you to some training or conference. In the worst case, your manager may not be able to help you, but at least (s)he is aware of your efforts, which may be a plus for you when it comes to e.g. salary negotiations :-)