Of course you couldn't have bless and SG up at same time. Never meant to imply that. Paladins cant cast cloud of daggers, of course its a teammate doing it. The Paladin part is never overshadowed in possible combos, it can always contribute. Its a team game.
The idea is that they cant escape SG in a normal move. They can crawl to you and attack, or just stand up. I have never seen that on the on the record, where is that. If that's the ruling that's absurd, especially in it application with haste.
Either way they can only move one square, so probably not out of field. If they use a dash great, they just wasted the whole turn to avoid taking damage next turn and you can just move the field over them. Usually they will just fight it out, taking damage at the cost of attacking you.
Spirit Guardians is a ridiculous spell to have going and worthy of building around since it damages whenever they enter on a turn, not a round. If you coordinate with the party they can push people into and out of the zone multiple times per round, piling up damage. Lightening lure can work, Dissonant Whispers, Gust of Wind, Hold Person, Plant Growth, Spike Growth, Thunder waves, grapples, shoves, difficult terrain etc, can all keep them in or put them in. The damage isn't much but its constant over a rather larger area to grind them down and half their speed. Its 15' radius up and down also, so it will affect flyers and those below you also. Once the team sees it in action, they will take steps to put people in it, counting the damage done as "their" damage done on their turn.
It used to be even better, you could run the zone over them and it would count, but this was changed (correctly for balance and intent) some time ago.
Considering all the other tools you get, adding auto-damage, speed reducing zones to Paladins is probably a little much. It takes some time to get but its worth it, especially if you plan to play through level 20. The other oaths help you mostly against single targets, Crown is for the masses of enemies although its fine against solos also. Its great for the Age or Worms path, with many Sons of Kyuss (and much more powerful versions) that just hurl kyuss worms at you all the time.
Back to the OP, Paladins also have a bunch of just useful and fun and unique stuff. Wrathful Smite is sort of crazy for a 1st level spell that's tacked on to a weapon attack, handing out disadvantage on all attacks and checks, it can take the teeth out of a lot of brutes. Free mount that you can always get back. You can interrogate people with Zone of Truth. Crusaders Mantle can charge up your allies and their summons or undead minions, if your DM rules it works with an ally's Animate Objects its crazy good. Aura of Vitality is 20-120 HP in healing for a 3rd level spell or 70-170 with one level of Life cleric. Flat out bonus damage at level 11 with the radiant type. Destructive Wave comes late (a Lore Bard can get it at 10th level, you don't until 17) but is very good, even at that level.
As a side note, for my son who wanted to play a Paladin like Reinhardt in Overwatch, I started with Thunderous Smite as a level 1 spell, then Thunderwave at 2nd level, and kept increasing damage and radius until I got to Destructive wave as a level 5 spell to simulate the Earthshatter ability. Eventually he found a magic hammer that gives him the Fire Strike ability, that just mimics the Wizard spell firebolt.
Although high level play is rare, Paladins have average to very good high level abilities and spells. The capstones are at least decent.
The Paladin toolbox is just huge and varied and useful and fun. Compared to the other martial classes there is just a lot there.