AWK is old. 1977 old. Later versions that appeared (nawk and gawk are the most common) helped make it a smoother language, but it's still a pain. There are definite features you will be missing in an awk script:
- Any useful data structure slightly more complex than associative arrays. Try multi dimensional arrays, it's actually fun to do. Once.
- Any useful programming construct to help manage with complexity of scripts longer than a few hundred lines. No classes, no variable scoping, no namespaces in general. Not to mention an extremely permissive compiler.
- Any easy way to deal with the environment (other than text). Try sending http requests in awk, it can be a pain.
In 2015, if you need to write a script you should almost always prefer python/ruby over awk.
Now if you're asking whether you should learn awk? It comes in handy. There are a lot of awk scripts in the wild, and you may need to read them or edit them one day. Also, awk has a fun way of parsing input, which makes for very enjoyable one liners. Learning awk (and some complementary utilities like sed or find) turned me into a "oh, it can be done in a quick one-liner" kind of guy. Definitely recommended.