I've always thought that Frieza was the most dramatically appropriate final boss for a series like Dragon Ball. An intergalactic tyrant who can not only destroy planets, but doesn't even see it as much of a loss because he has a million more under his thumb. A man who enslaved the race that both the main hero and the previous arc villain belonged to. A man who is justifiably overconfident on the grounds that, despite ruling an entire galaxy, he has never in his life encountered anyone strong enough to even leave a bruise on him, let alone be a threat to him. A man whom the entire galaxy bows to, lest they be obliterated in an instant. Frieza was a god in everything but name.
Compared to all that, the androids and Cell just seemed like random mooks who were only considered a bigger threat because they arbitrarily had a higher power level. And then it's revealed that that's exactly what they were: creations of the mad scientist of an army that Goku had long since defeated and surpassed. You can't even visually show that they're stronger than Frieza because Frieza could already do the most visually impressive thing possible: wiping out a planet with a move that only uses one finger.>>64004305>Past Frieza (literally the instant Goku becomes a super Saiyan, notice the theme here?) though, the idea of winning through technique or skill is pretty much thrown out the window and it becomes who's the strongest with no finesse or technique required beyond throwing energy blasts
Also this. Even after becoming Super Saiyan, Goku still needed to use some strategy to beat Frieza. After that it just became about raw strength and nothing else.
tl;dr series should have ended when they left Namek.