The people telling you to play a caster are assuming you want to farm for gear with them and then play the other classes. Competitive protocol (for instance at the start of ladder) is to make a sorc because she can wear high MF gear with no loss of power and farm areas / bosses the fastest.

If you're just starting out, you don't need to be thinking about that stuff at all, and nor should you. If you like the Paladin, play it. Fuck one up. Use the wrong items and skills. Learn how it works! Then someday when the honeymoon phase with the game is over you can respec and make a god tier paladin decked out with gear found on another char.

That said, Paladins are perfectly viable through the whole game with self-found items. Keep at it!