DBZ rewatch episode 20-29.
There it is! There's the lengthy scenery pans, long powerups and the drop in animation quality.
To be fair, episode 21 was by far the nicest animated and every episode has some really nice art. I love how the auras are drawn much more rather than the occasional CG effects that are used currently. Goku trashing Nappa was really rewarding and I still love how the Kaioken looks and how it's one of the better explained and balanced powers in the story starting from Z. So cool.
There are so many spoilery titles, though. Just look at them:
23: "Yamucha Dies! The Terror of the Saibaimen"
24: "Farewell Ten-san! Chaozu's Suicide Strategy"
25: "Tenshinhan Cries Out!! This is My Final Kikoho"
28: "Ferocity of the Saiyans! Kami-sama and Piccolo Both Die"
I really like how Piccolo teaches Gohan as he fights and how Gohan does end up attacking on his own. Piccolo's sacrifice, aside from looking great and giving me massive 90s anime nostalgia because of the style of it, gave him a good character arc. Tenshinhan's and Chaotzu's sacrifice was touching. The story's plenty good at character writing. That said, apparently episodes 9-18 are mostly filler so I probably wouldn't have cared nearly as much for Piccolo's sacrifice in the manga. That stuff helped a lot.
It's pretty obvious why it got so popular, but also why Z could be enjoyed without seeing the original Dragon Ball. The characters' personalities are spelled out well. It's entirely concerned with just telling a story. There's basically no fanservice, the story is basic enough to understand and it's not strange enough to alienate people from other countries who have never seen anime.