I would say that I find the example unconvincing. Smite is indeed a powerful action economy use but only a subset of combats start with point blank swinging. So, a paladin can bless before they would be smiting and so the bless becomes the "better action economy" because you get its benefits round after round for free for only one slot. That d4 bonus to the saves combined with a decent Con (perhaps Warcaster) helps keep that benefit going for not just the pally but as you say others.So
I *think* most people will agree that the Paladin is a very powerful class in 5e - perhaps one of the few that are probably a little bit OP (esp in a game with few combats per long rests).
A big part of that is the power to smite - to "burn" spell slots to do more damage when hitting a foe with a weapon. At first glance, this seems like an inefficient use of spell slots. For example, a paladin could cast bless and give +1d4 to hit to 3 people (including herself). If *two* more attacks land in a fight that would have missed without the bless spell (a reasonable number), those 2 attacks will probably do more damage than the 2d8 that spell slots would have done if, instead of being cast as bless, was used to power a smite.
Yet, despite this, both from personal experience as a GM running a game with a paladin, or from reading the boards here, a paladin smiting away is a thing to behold. WHY?
Because while it's not very "efficient" to use your spell slots as smite, it's very efficient *action wise*. Casting a spell takes an action usually. An action you could use to attack instead. Smiting allows you to use your spell slots and attack at the same time.
It's one of the reasons I'm becoming a bit hesitant about the hexblade after using it for a while in a pbp game - every round you cast is a round you are not attacking (or vice versa)*. That is what the "gish" in pathfinder was (the magus) - a class that could cast and attack in the same round, and why it was very powerful indeed.
So that's why the Paladin is good
* the hexblade *can* take an invocation that allows him to smite like a paladin, but he only has 2 spell slots for 90% of most campaigns, so it's not so great - and it's an invocation he can't use on something else.
So, I do not disagree on the pally effectiveness or its standing and nova potential. But, the case for action economy of smite vs bless is not that solid in a lot of cases.
Of course, this will vary by table to table - being directly tied to the frequency of "sudden combat onset syndrome" and "short fights".