I don't think the design intends that monsters continue to be used, but in larger number. The design ALLOWS it, which is different.
Edit: I also think that if you are doing that just so fireball can work, that just proves that fireball doesn't work right.
Considering the designers
explicitly said that's what they intended people to do...I don't really accept that.
No, it wasn't.
It was to try and strip back the burdensome and restrictive rules to something looser and more flexible.
I'm more inclined to trust the many, many, many times they said that that's what they were aiming for, over this claim.
Especially since "burdensome and restrictive rules"
still absolutely applies to 5e. Just ask anyone who's tried to squeeze a gritty survival story out of it.
If "remove all burdensome and restrictive rules" were
actually 5e's core design goal, it has objectively failed.
Kinda.
4e did that with minions. But they ended up with. Boss ogre for lower levels, normal ogre for mid levels, and minion ogre for high levels. Which was pretty awkward.
See, I hear this a lot, but nobody ever actually goes through the numbers to describe what they're talking about in order to show this effect being "awkward."
You can, quite easily, use monsters from level+4 to level-4, a
nine-level range, entirely as standard creatures, no need for Solos or anything else. So where, exactly, is the problem here? Because people are already saying that a (roughly) six-level range is normal for a 5e monster...
and that's exactly the same as nine levels in 4e.
Minions and Solos just let you expand that range
even more. With them, you can have creatures that WOULD be totally impossible for, say, a level 3 party--a Fire Giant, say--act as an actually reasonable threat for a couple levels. Then you use the original non-Solo monster for ~9 levels, if you really feel like it. And then, when they're now genuinely so fragile that the party actually can start dealing with them in only 2-3 hits, you can Minion-ize them (or use the "Mook" rules I've seen, where Minions are one-hit-wonders and Mooks are
two-hit-wonders, and make for a clean, smooth progression from Solo as an x4, Elite as an x2, Standard as x1, "Mook" as x1/2, and Minion as x1/4.)
I would also like to note, for the record, that I was
not the person who brought 4e into this discussion, and would not have done so myself; I am only
responding to someone else bringing it up.
So with 5e they wanted to keep AC and to-hit a lot more restrained. Now a goblin can still stab a level 20 fighter.
Really? Because a CR 1/4 Goblin from the 2014 MM has +4 to hit. I assume you used Fighter as an example of a high-defense character, so I'll be presuming a "tank" character here. Plate is base 18, assume at least a +1 item has been obtained (despite the hatred of magic items from much of the 5e DM community.) Shield is another +2, won't assume a magic item there. Defense is another +1. That's AC 22. Meaning this goblin can only hit on 18-20. Is that really "can still stab a level 20 Fighter" to you? Because if it is, 4e really wasn't that far off mang!
That was the idea.
Better spells exist now eg spirit guardians.
Copious healing as well. Hold your spell heal afterwards if required is better meta approach.
Well. At least
someone admits that's the line Wizards fed us during the "Next" playtest.