The repetition doesn't stop there, the show also reuses a lot of animations, which is a common practice in anime but can get annoying when it's overdone. You'll see Kenshiro using the same moves over and over again, ripping his shirt(s) again and again, and the show will often reuse the same stock footage of characters screaming and punching the air. This just adds to the overall feeling of sameness that permeates the show.
Now, let's move on to the supporting characters. Bart is supposed to be the comic relief, but he's just not that funny. Lin, on the other hand, is just a damsel in distress to be rescued by Kenshiro. She's merely a helpless girl who constantly puts herself in danger, and it gets old after a while. Mamiya was initially presented as a strong and independent woman, but her character development is stunted and she eventually becomes more of a love interest for Kenshiro. And Toki was just a Jesus Christ
Rei is probably the most interesting supporting character, but after his story ended, he was reduced to being a sidekick to Kenshiro. His initial storyline about searching for his sister's kidnapper and avenging his parents was intriguing, but then I guess the writer ran out of ideas for him.
As for the villains, there are a lot of them, but most of them are forgettable. They're just there to be beaten up by Kenshiro and move the plot along. The three main villains who are actually related to the main plot are Shin, Souther, and Raoh. Shin is the best of the bunch, with a tragic backstory and a personal connection to Kenshiro that makes their fights more meaningful. Souther is an interesting character as well, but his motivations are a bit muddy, and he doesn't get as much screen time as he deserves. Raoh is a 'big bad' dark messiah dictator who is there to be defeated by Kenshiro in the end.
In terms of animation and music, the 1984 Fist of the North Star TV anime is acceptable but not exceptional. The animation was decent for its time, but it doesn't hold up well compared to modern anime. The music is forgettable, with a lot of generic rock tracks that don't add much to the show.
Overall, it is badly written, with retcons and plot rehashes that make it hard to watch after King arc (the first arc). It has some interesting ideas and characters, but it's hampered by its repetitive formula and lack of depth. If you're a fan of classic anime or martial arts stories, you might enjoy it. However, if you're looking for something with more substance and originality, you might want to look elsewhere. I would recommend the more recent pentalogy (3 movies + 2 OVAs) if you want to explore the main plot with a more streamlined presentation and the retcons were fixed by adding foreshadowings.
