I believe shields in this game need to be rebalanced, in 2.0 they were strong, giving PLD an edge as MT, but due to the adjustments in 3.0 a shield is basically a glorified parry and offers no real advantage, which defeats the point of it even existing. So here is my suggestion to rebalance shields.

1. Remove the block strength and block rate stat:
These stats do nothing anymore other than nerf the strength of an underlevelled shield. Instead I believe shields should have a static rate and strength based on type.

e.g. Buckler = 40% rate and 20% strength, Kite = 30% rate and 30% strength, Tower = 20% rate and 40% strength.

This simplifies block mechanics based on the type and not the level of the shield. Instead the level of the shield will only give extra stats like all other gear in the game.

2. Add physical defence to shields:
So instead of leaving the space where block strength and rate used to be empty, put some extra physical defence on shields and add the shield type (buckler/kite/tower) in that space. Having extra physical defence will help secure the idea that PLD is the physical tank. Conversely adding some magic defence to great swords to secure DRK as the magic tank.

3. Massively increase the enmity generation of shield swipe:
PLD has the worst enmity of all 3 tanks as it has the lowest damage and it's enmity combo is not it's highest damage combo, so while DRK and WAR can comfortably hold hate out of their tank stance a PLD is far more likely to struggle.
Shield swipe is only ever going to be used when the PLD is getting hit, so likely only when the PLD is tanking. I think shield swipe should generate a huge amount of enmity, enough to secure the PLD hate for a long time. I'm talking a large enmity spike, a sword oath shield swipe should generate as much enmity as a shield oath Rage of Halone.
This will help PLD tank in sword oath easily to make up for it's lower damage, while the power of the shield will allow it to tank in sword oath with less risk. Making PLD a stronger MT without taking away from it being weaker than the other tanks and emphasising it's defensiveness only against physical mobs as magical ones won't proc shield swipe and can't be blocked.

4. Adjust blocking and casting:
PLD is the only tank that has long cast times and the only tank with a shield, so these cast times should synergise with shield use.
You should be able to block and parry while casting, but not only that, if you block or parry while casting it will prevent your spell from getting interrupted.
So for a tank buster a PLD could put up rampart and Shelton then begin pre-casting clemency or stoneskin, the tank buster would hit, the PLD would block with Shelton, their clemency/stoneskin would not be interrupted thanks to the block and then it would go off, healing/protecting them from an attack after the buster.
Currently, if you are casting you cannot block or parry meaning PLD using it's spells takes away from it's defensiveness, which makes the spells less desirable to use as they may get interrupted meaning not only did it do nothing but it reduced your chance to add some extra mitigation.
I think that shields should enhance casting, rather than casting taking away from shields.

Finally a wider variety of shields is needed, I think relic should always be kite, tomes should always be buckler and raids should always be tower. And a variety of each should be available from crafting or other content like Primals, maps, diadem, palace of the dead, etc.
Basically everything at endgame is kite shields and this further reduces the point of having different types of shields available.