In D&D 3.5e, blasting was known to be a comparatively weak strategy for a Wizard to adopt. On the other hand, in D&D 5e, there have been a number of changes that potentially render it more effective, for example:
- The numbers on blasting spells have been adjusted.
- Spell resistance has been changed to 100% chance for 50% damage instead of ~50% chance of 0% damage.
- Summoning and polymorph options have been severely limited.
- Specialising in Evocation gives strong benefits to blasting spells.
So, is blasting a suboptimal strategy for a D&D 5e Wizard? A good answer will be able to objectively demonstrate that this is or is not the case compared to 3.5e, or that something else is different between the two editions which alters the situation.
Best Answer
Compared to 3.5e, it is a less suboptimal strategy, for the reasons you mention, as well as a few more:
With all that in mind, I would argue that at low levels a blaster isn't suboptimal, because the options available aren't significantly stronger. However, by the time options expand with 4th-5th level spells or so, the same issues arise, even if they are lesser.
As an example of the kinds of spells that work about as well as they did in 3.5e, take wall of force. Splitting an encounter in half is almost always better than dealing damage, unless the encounter would have been no challenge anyway.
Note that even a very optimized 5e wizard will probably include some blasting in their repertoire, and more so than a 3.5e wizard might. This is because quite a few buffs, debuffs and control spells now use the concentration mechanic, which means they need something else to do when they already have one concentration effect active.