Morkus from Orkus
I disagree. You can move and get full attacks and it's better for you to take huge chunks out of their hit points and let the fighter do clean up with his attacks, taking the enemies down. You get much better use of your smites and the monsters drop faster. IIf you change to a different foe to get more damage you are giving up action economy. That is generally not a wise choice.
It's a team game, the party should play like a team.
If you're fighting kobolds you are likely level 1-3 and have very few smites. It doesn't matter anyway. So the fighter is better when you are fighting small, weak enemies and the paladin better at tougher ones. It's give and take, which is fine. Classes can be better than one another under different circumstances. That's the game working well as far as I'm concerned.That depends entirely on what you are fighting. If you are fighting kobolds almost every single smite die you use is going to be mostly wasted.
Overall, though, once you get past level 2, you tend to find a lot of monsters with significant numbers of hit points and the paladin can use his educated guesses to maximize his smites.