I disagree on the bolded bit. I think that players who go into wizard know that they will be squishies, compared to 3.5 wizards they are downright hardy. The damage dealing isn't really the prime problem though IMO. If you look at any wizard guide going back to 3.5 you will see terms like Batman/god, controller, summoner, blaster, & maybe a few others. The Wizard was never really top notch at blaster (sorc beat them handsdown & had a better toolbox). Summoner was always a divine caster wearing the crown. Controller fits many classes situationally & can be ignored. The God wizard was like batman & has two or three prime duties in the group, allowing everyone around them to be even more awesome, making opponents less awesome against the wizard's allies, and having the tool the party needs now (or at least "after we rest so i can change my prepped spells") in their toolbox.@Leatherhead − good point
The most popular choice of subclass for a Wizard character is:
• Spellsinger 14%
• War Magic 14%
• Evocation 13%
• [probably Divination circa 12% because Portent for combat]
This suggests that the golden majority of Wizard players are frustrated with the Wizard class, and seeking options elsewhere.
The main dissatisfaction with the Wizard class for Wizard players, appears to be, the lack of combat survivability and the lack of damage dealing.
Say what you will about the pros & cons of concentration, it unquestionably removes much of the wizard's ability to act as a force multiplier & make the party awesome unless you are a sorc with twin spell. That leaves the flexibility of having a spellbook and ritual spells. The scorlock could pretty much rival a wizard's capability of having everything in their back pocket if we can wait for tomorrow without needing to rest & reprep spells; but scorlock does it without needing to really sacrifice much, without needing to sink amounts of money that make equipping an all strength based heavy armor party look modest into scribing spells while gaining a bunch of multiplicative power bumps... with these new abilities sorcerer & warlock both gain the ability to have the spell tomorrow and don't need to invest the gdp of nations into a spellbook.
Finally you have the wizard's ability to ritually cast spells scribed in their spellbook without needing to have them prepared... This is great and all, but there are a total of nine ritual spells level 4-9 & only 6 of them are on the wizard list but tome pact warlock could already have all nine. Moon druid faces a similar problem as a wizard who thought ritual casting was important with cr3+ beasts being either too big for much use or mistyped as monstrosities.
Wizards used to get bonus feats, but now not only are they not feats at all... they are almost all warlock invocations & warlocks get them exactly like wizards got bonus feats.
In short, the UA completes the cycle of giving scorlock the "meat & potatoes" of the wizard class & wizards never really got a new bone to support their table as the legs were slowly given to scorlock.
edit: There is also the role of skills & sidelining of int as a meaningful stat while elevating charisma