Too much burst champs in the game at the moment. That's because best CC for the enemy is death, and it's reather easy to pull off.
Sure we have assassins, but most of them are high risk high reward, and that's how it should be, but of course there are non assassins that ignore this rule, like trynda, twitch, now Morderkaizer, kayn, most of the mages.
They're good enought that they've taken support role for themselves (mostly mages) just to have more burst in the game. Cuz again death is best CC in the gaming industry, and since it's burst good luck their target to react or their teammates to react and counter those burst champs in those 0.1-0.5 sec window you have before the target is dead. If they're assassins they have built in invis which is now uncounterible, stealth is but you're not gonna see someone like twitch when he can burst your entire team far out of your range. Stopping trynda is utterly impossible without good CC and even then he still has his ult when or spin to take one of you down ATLEAST with him. Usually 3.
If you would take something like Jhin, a burst dmg marksmen, he's still kinda lame. He has no escapes, a single one decent CC that requires you to stand still (at that point you might as well serve yourself on a silver platter) and while movement speed from his passive scaling with aa speed is sweet for chasing less mobilechamps, it's absolutly useless for kiting, due to assassins having better mobility, aka. dash, burst mages, some sort of hard CC to keep you in place, or bruser type of bursts a good mobility skill and a decent soft cc.
before you go saying "buy GA" we all know that it will only prolong the inevtable (insert thanos meme here).
what't i'm trying to say is that, sustain damage has the short end of the stick mainly because nowdays where enemy most champions requiring only fraction of a second to kill you, it takes too long for you to do anything else apart from let it happen, because till you reach their levels of damage you're 5x dead already.
That's why atleast in my games, i see less and less actual marksmen dueing with support and instead i see burst mages or something that can actually take the beating atleast for little longer.
It doesn't even take alot of gold to blow someone up with burst, most assassinst can do just fine with just dusk blade vs someone squishy like an adc who might have way better score then them.
I guess i just with you'd actually had to work for the damage you deal to the enemy and actually work for a victory instead of just clicking few buttons on the enemy before enemy does it on you.
P.S. I abviously didn't mention all burst champs. I expect you guys to know them by now.