The reverse, however, does hold: a Paladin gets a lot for one or two levels of fighter. Fighting Style, Second Wind, and Action Surge are all very good. Compare a Paladin 12 / Ftr 2 that has the TWF Fighting Style with a Paladin 14.
Sure, it looks nice at 14th level. But let's look at the whole level range.
The multiclasser brings +1 AC, Action Surge, and the ability to get TWF which isn't among the style options for paladins. The last is notable at 4th level because TWF is busted at low level, and at levels 13+ because it synergizes nicely with Improved Divine Smite. The multiclasser also gets Second Wind, but this will rarely see use above low levels since it is competing for bonus actions with TWF and it only ever heals 1d10+2.
What does the straight paladin get to compensate?
At 4th level: Channel Divinity and an ASI.
At 5th level: An ASI, Extra Attack, and 2nd-level spells.
At 6th level: Extra Attack, 2nd-level spells, and Aura of Protection.
At 7th level: Aura of Protection, and that aura gets a major boost like "immune to charm" or "resistance to spell damage."
At 8th level: Boosted Aura of Protection and an ASI.
At 9th level: An ASI and 3rd-level spells.
At 10th level: 3rd-level spells and another aura boost, granting immunity to fear.
At 11th level: The immunity to fear boost and 1d8 bonus damage with each attack.
At 12th level: 1d8 bonus damage with each attack and an ASI.
At 13th level: An ASI and 4th-level spells.
At 14th level: 4th-level spells and the ability to remove hostile magic.
At 15th level: The ability to remove hostile magic, and a super-powerful defensive ability (e.g., regenerate ~10 hp/round whenever you're at half hit points or less, or permanent disadvantage to hit you for most of the high-level monsters in the game).
At 16th level: The super-powerful defensive ability and an ASI.
At 17th level: An ASI and 5th-level spells.
At 18th level: 5th-level spells and a 30-foot aura.
At 19th level: A 30-foot aura and an ASI.
At 20th level: An ASI and 1/day god mode.
At levels 5, 6, 11, 12, 18, and 19, the straight paladin is better. Extra Attack, Improved Divine Smite, and Aura Improvement are killer features for the paladin that trump everything fighter 2 brings to the table.
At levels 4, 9, 10, 13, 14, and 17, the multiclasser is better.
At the other levels, it's debatable.
All in all, it lines up pretty well. And note also that much of the multiclasser's advantage at 13/14/17 depends on exploiting the benefits of TWF with Improved Divine Smite. If feats are in play, the straight paladin could pick up Polearm Master for a bonus action attack, and most of that advantage would disappear.