I've cycled through a bunch of all-out-damage, glass cannon builds (Spriggans/Spinners + Damage Sets) to try to counter a lot of tanky players in heavy armor and get kills, but they just laugh off damage. It would be really nice to be able to counter tanky builds when you go all-out damage and leave yourself so vulnerable, but it's just not worth it. Too many players have high resistance, high health, and HOTs.
On a full damage build you can only kill the "bad" players. Everyone "decent" or better are just too tanky.
It may not be fun for you, but its fun for others. Also, stacking pen/weapon damage/spell damage/max mag or stam is a good start against tanky and high health targets but it is only part of the equation. The whole point of stacking those things to boost your damage, is so your burst combo hits as hard as possible, and eats as much of their health as it can in a short amount of time, so they have as little opportunity to react before you can execute them. Without a good burst combo, stacking for high damage is essentially worthless. It's like having the best quarterback on your team that can lob the ball to any target, and he always throws the ball to the slowest player on the field.
Another thing people forget, especially people new to PVP, is that ESO PVP is fundamentally a war of attrition. Newer players don't learn this until they get more experience PVPing, but often times your 1st or even 2nd attempt at burst comboing someone down can fail. That is normal! The goal here is for your opponent to run out of resources before you do. Because once you have no mag to heal, no stam to dodge roll or block...then you better LOS or get out of that fight because you're open to CC, or someone ult dropping on you.
With that said, in the tank meta we're still in some targets just can't be killed alone. That's just how it is. Some targets need a multiple people burst comboing at once to take down. You really have to learn to pick your battles, because if you try to take every single fight that is presented to you, you may lose most of them. Coordination goes a long way in PVP, so any opportunity to focus fire a target with someone else (even if they are not grouped with you) take it.
There are many more nuances to PVP, but the basic starting point would be this:
Pick a target you think you can kill > Pre buff yourself > Debuff your target > Go in on them with your opener > Hit them with whatever stun you've slotted > Go in hard with whatever your burst combo is > Ult drop or use whatever execute ability you've slotted to finish them off. Hopefully they didn't stun break and heal themselves, but if they did no biggie just back off, replenish your resources and try again. That's the basic flow of PVP.