And 4e mosters, at first level tended to have 30+ hps, while 5e monsters might have as few as 3 or, perhaps, 10 or so. So, relative to what you're shoot'n at, that's more like /doubling/ damage.
That's a bit of an unfair comparison though.
1st level 4E is more comparable to 3rd level 5E. 4E was purposely designed this way to bypass the learning stages of level 1 and 2.
The monsters have more hit points, but so do the PCs. The PCs do more damage as well at low level.
And in fact, many 5E low level monsters are more like minions or tough minions (i.e. in our 4E game, tough minions took 2 hits to kill). Hardly the same challenge level as most 1E through 4E low level monsters.
5E is like a turkey shoot for spell casters and non-spell casters alike. They just don't heal that well when they get shot at back.
Then look at dailies. A 5th level daily might do 3d6+bonuses in 4e, in 5e it does 8d6. And, you get more of them as you level, not just 1, and you can hot-swap it with any other spell you have memorized, and swap those with any you know with an extended rest. That's compared to swapping out your 1 fifth-level daily for the one alternate in your spellbook (2 with a feat) only when you take an extended rest. The flexibility and power of neo-Vancian casters is off the charts compared to 4e.
Yes, 5E Fireball is a bit unreal at either 14 or 28 average damage, but then again, a 5E 5th level fighter gets 3 or more attacks, often hitting and often doing 30 points in a single round. Round after round after round. And Fireball still has that pesky targeting issue.
One aspect of 5E casters though is that they really do not have more spells per level. Even if they go offensive with every single spell at level 5, that's 10 to 12 non-cantrip offensive spells and a boatload of cantrips. In 5 encounters, 4E wizards get 10 encounter, 2 daily and 1 utility spell plus their at wills (which end up being more at wills than 5E because wizards get bonus non-damaging at wills like Prestidigitation). It's not that much different. 5E casters do have more flexibility, but then again, many of the 4E powers do more than just damage. At level 20, it's 22 to 32 Dailies for the 5E caster, and in 4E, 29 encounter, dailies, and utility powers in 5 encounters (not including bonus stuff from feats, themes, items, etc.). The number of non-at wills that each can cast is comparable, the 5E just does have more versatility with more to choose from.
But Vancian was a dinosaur. Neo-vancian needs something to offset it. Easily saved spells, even for high level on and fewer of them (and wimpier in some cases, stronger in other, but not by too much).
Just about any tier 1 class was very broken in 3e, yes. But, the flexibility granted by Neo-Vanican, and the addition of at-wills makes it anything but clear that 5e wizard is lagging the 3e, relative to the kinds of challenges he'll face.
I can agree with this. 5E monsters seem wimpy. But 5E PCs seems fragile over multiple encounters.