Honest question for those who want to nerf Divine Smite so bad: Have you actually broken down the numbers? Specifically vis a vis the Fighter, whose toes so many of you guys seem to believe the Paladin steps all over?
Let's compare the two at Lv. 17, in fact. Greatswords, Great Weapon Fighting Style.
The Paladin at that level has 3 4th-level and 1 5th-level slots. Can attach maximum-damage Smites to both hits 2 rounds per day. Assuming neither crits, that's, at most, an extra 45 avg. damage (5d8 + 5d8) in those rounds. Any other two-Smite turns that day will use lower-level spell slots for less damage.
The Fighter (Battle Master) at that level can add on an Action Surge turn: 3*(2d6r1&2 + 5) = an extra 40 avg. damage at the bare minimum. More than likely, that Fighter also used at least a Superiority Die or two. Just one of those used on an on-hit maneuver (1d10) puts that at 45.5, already ahead of the Paladin. More typical is 2 Superiority Dice (51) or even more. And the Fighter can do this 6 times per day, assuming 2 short rests, and never suffer a drop in damage output from lower-level slots like the Paladin does.
Oh, and I didn't even account for the Fighter taking Great Weapon Master and using the -5/+10 trade on that Action Surge. If so, that Action Surge adds an extra 30 points, bringing the totals to 70 (minimum), 75.5 (1 on-hit SD), 81 (2 on-hit SD). That's on top of the 70 the GWM Fighter was already doing without Action Surge. That Fighter is probably saving much of its Superiority Dice for Precision Attack to actually ensure most of that damage, too. Also since the Fighter gets 3 attacks and the Paladin 2, on its at-will turns the Fighter benefits more from GWM because that 3rd attack is another opportunity for that feat to add its damage.
Sooo ... yeah, I'm not seeing this problem of the Paladin stepping all over the Fighter, or even stepping on its toes at all. It's just not happening. The only time I can see a Paladin's Smite turn surpassing a Fighter's outright is if the enemy is paralyzed for auto-crits, which doesn't happen much if at all once you run into bosses with Legendary Resistance.