The wide majority of infantry suits have:
Poor shield regeneration values
Very long shield delay/depleted delay times
The damage profiles on weaponry(and the trend of ridiculous high alpha damage plus this the stealth abuse issue in this game) make it so that nearly all weapons can have a vicious effectiveness on shields. It wouldn't make sense for a 60 point damage gun to have 30% more power against shielding when shields have the disadvantage of less HP and the gun is already so powerful.
You need to have high shield HP to live, to improve your bad shield delay, and your bad shield recharge value.
Three modules you need to get for basic survival when shield tanking, which is a heavy investment.
With armour on infantry, you have:
Ability to round up a very large sum of HP in armour
No weapon has any extreme damage profile advantages against armour besides explosives, which not many people use in the first place.
Some modules don't follow the more HP layout of armour, and this allows shielding modules to give more HP than them (e.g., reactive plates)
Regardless you can get past this.
Some suits can tank enough armour to match that of a heavy suit, be only a little bit slowed, and once you have 10 HP/s in armour and up you can have better survivability than shielding(because of how armour regeneration being quite close to instant on infantry where shielding you have to wait often over 3 seconds, which is enough time for someone to find and kill you)
Besides this, you hardly need to invest in modules or skills for armour.
There has been recent high HP stacking of shields, but as stated before the weapons can combat this easily.
With vehicles there's this:
Unnecessary AV buffs and many cutoffs from vehicles have made it so that survivability is really low unless you have level five in most of the shield tree.
Shields on vehicles cannot have their delay time changed, only depleted time, and cannot improve recharge time unless you have proto shield boosters.
The wide majority of AV methods have affective damage profiles against armour.
Swarms and forgeguns are actually effective ways of fighting shields, because swarms are universally overpowered at basic+ and all advanced+ forgeguns are quite a bit ridiculous, especially because of their range.
They can survive Unfair methods of AV like steathily planting RE's on them, unless if they were advanced+ and the vehicle wasn't slightly dual tanked when fluxed. Jihad jeeping is a may thing.
Armour on vehicles, at armour regeneration at five and with other things it may be possible for you to outregenerate the damage, but it will take heavy SP cost.
The wide majority of AV methods are hypereffective against armour based vehicles.
Impractical methods like steathily throwing RE's and jihad jeeping can be done with little to no difficulty and can take ground out then and there. They may be able to survive jihad jeeping.
Dropships are a no go, because unless you are using something like complex CPU/PG upgrades to tank as much HP as possible, they are far too slow to survive.
ADS have better maneuverability, but as they have less HP and very butchered levels of pg/cpu(like most of the vehicles)
it's possible for a swarmer to down them in all 3 volleys, and this can usually be done in 4 seconds or less.
Because of the swarm launcher having an excessive lock time, like how forgeguns have an excessive effective range, it is usually not possibly to escape without an afterburner, hardener, or booster. Swarm users often, even with these things, get the third volley to fire(because any tiny bit of skilling into swarms will make the lock on time less than one second.) Besides this without proto or so it will take time for the module to recharge, keeping you out of the battlefield for quite a bit.
Caldari ADS have the same issue as the other caldari vehicles and same for the gallente ones.
Unless you don't have your gallente vehicles hyped up on regen they won't outperform the caldari ones.
Regardless, Shields and armour for everything is in a bad state.