As others have said, "is [style] good?" is a really tough question, because it depends so much on your school, their curriculum, your teacher, you, what your goals are.....
If your goal is to get in shape and be a competitive athlete, and you're at a good KKW/WTF-style TKD school that has high standards, does a lot of sparring and sends people to tournaments and such, then yes, Taekwondo is great. It's even in the Olympics. On the other hand, if your goal is to learn the kind of self-defense you might need to defend yourself while working as a prison guard, that same school might not be so great. And whatever your goals are, if the school/teacher/chain doesn't teach well or have high standards, your training won't be good - and that will be true in any martial arts style.
At it's best, TKD will give you great kicks, good hand strikes, good flexibility and cardio, and some decent sparring experience that will help you with things like distancing, managing your energy, handling pressure, etc. TKD is a striking-focused art, though, so there are some limitations involved in that. If your main goal is to learn to defend yourself, you might want to try also learning a grappling-based art like BJJ, Judo or Hapkido at some point. But that doesn't necessarily mean giving up TKD, unless your financial situation means choosing one or the other.
If your goal is to get in shape and be a competitive athlete, and you're at a good KKW/WTF-style TKD school that has high standards, does a lot of sparring and sends people to tournaments and such, then yes, Taekwondo is great. It's even in the Olympics. On the other hand, if your goal is to learn the kind of self-defense you might need to defend yourself while working as a prison guard, that same school might not be so great. And whatever your goals are, if the school/teacher/chain doesn't teach well or have high standards, your training won't be good - and that will be true in any martial arts style.
At it's best, TKD will give you great kicks, good hand strikes, good flexibility and cardio, and some decent sparring experience that will help you with things like distancing, managing your energy, handling pressure, etc. TKD is a striking-focused art, though, so there are some limitations involved in that. If your main goal is to learn to defend yourself, you might want to try also learning a grappling-based art like BJJ, Judo or Hapkido at some point. But that doesn't necessarily mean giving up TKD, unless your financial situation means choosing one or the other.