Updated: Jun 15, 2020
By definition, a "martial art" needs to include both the "artistic" as well as the "martial" ("warrior-like") sides of the discipline.
If a style focuses only on the artistic, philosophical or spiritual side, it's not a real "martial art," it's just art, plain and simple. Nothing wrong with this, art is beautiful and necessary for the soul and culture.
However, if you're attacked in the streets, you won't be able to use your skills to defend yourself and those you love using only art.
On the other hand, other disciplines —like boxing, wrestling, MMA and some styles of Brazilian Jujutsu— generally focus on the "martial" side.
These styles are excellent at teaching fighting skills, but they're generally weak on the "artistic" (meaning philosophical, ethical or spiritual) side of martial arts.
This may cause problems with some practitioners who could become "bullies", since their training lacks the ethical component to tame aggressiveness.
Some practitioners of tough styles criticize traditional martial arts for considering them soft and ineffective, and unable to test their effectiveness.
At the same time, some traditional martial artists dismiss fighting styles for lacking the ethical, cultural, and philosophical side of martial arts.
Both sides, however, agree on accepting Kyokushinkai Karate as one of their own.
Yes, Kyokushin is a tough karate style, maybe the toughest there is ("Strongest karate", as founder Mas Oyama called it). To prove yourself you need to spar, full-contact, often times against several opponents in a row. Many Kyokushin practitioners became famous MMA and Kickboxing profesional fighters.
However, at the same time, Kyokushin is a full-blown traditional karate style. It shares all the same features one would expect from classical karate: ceremonies, respect, philosophy, ethics, bowing, katas, kihon, karategi, belt colors, ranks, Japanese culture, and so on.
Both the "Martial" and the "Art" sides complement each other at an equal level in Kyokushinkai Karate, to form well-rounded martial artists.
So, in short, Kyokushinkai Karate is a well-balanced discipline, the real deal. An authentic "Martial Art".