When I first heard about them I assumed that they would be used to augment your own personal damage within the vicinity of where you are and that overall base defense would continue to be handled by the regular turrets we’ve had for ages now.
If they were implemented that way, that would be perfectly fine. However they are implemented, in the skill trees, identically to other weapons. As such there is the expectations that they perform to the relative level of other weapons as they require identical investment levels of skill points. If they were, say, a bonus to the "Yeah Science" skill instead of their own standalone skill you'd see highly different expectations of them.
But as things are, they are positioned as if they are full weapons and thus I expect them to perform somewhere in the general viciniity of the efficacy of other weapon specs with their own advantages/disadvantges/unique quirks/playstyle.
Why anyone would abandon the regular turrets and try and use junk turrets for base defense instead is something I’m struggling to understand.
I'm using the Junk Turrets as if they are the weapon I specialized into just as I would with AK or SMG or Marksman Rifle. I do not expect them to pull the entire defense alone. I'm a base builder by nature and I expect spike traps, electric fences, electrical turrets, and strong walls to pull alot of weight. However I do expect them to contribute relatively the same amount of defense power as other weapons you can specialize in and not be completely left behind since horde night is a pivotal core aspect of the game.
If junk turrets are to be elevated to the same level as regular turrets then why have regular turrets?
Junk Turrets are limited to 2 and Electrical Turrets are not. As mentioned above I don't expect any weapon to carry the defense on it's own, though I will acknowledge that some (like Machine Guns) definitely can. Thus it's not a competition between turrets, they are intended to work together and my current INT playthrough has 4 Shotgun turrets already placed and 2 Auto Turrets on the way to compliment my 2 Junk Turrets (along with a couple electrical fences). If you have the ammo for it you can have 10 Electrical turrets shooting shotgun shells and 9mm. No matter what you will only ever have 2 Junk Turrets, perhaps 3 if you use a handheld one too.
Electrical Turrets also have a much greater ammo capacity and so allow you to personally free DPS as they can fire for minutes at a time, electrical Shotgun Turrets are actually pretty darn efficient on Ammo when you consider the availability of paper. It's almost exclusively just a question of mining gunpowder and lead. Auto Turrets go through 9mm ammo pretty quickly and in A17 that was a real issue but in A18 brass is everywhere. That being said, splitting between the two turret types pretty much keeps your only limitation being how fast you can farm gunpowder and this could easily be the gameplay style of an archer. Electrical Turret Ammo concerns only happen when you use them in large amounts of you use the same ammo type. Same ammo type is not a concern of perception/fortitude/agility (if archer).
It should be noted that 2 shotgun turrets is slightly less than the DPS of junk turrets but that 2 auto turrets is slightly more.
Or am I misunderstanding and people are complaining about the regular turrets on horde night?
You are not misunderstanding, they are talking about Junk Turrets. The easiest way to understand the limitations of Junk Turrets is unfortunately just playing a full play through with them AFTER playing a full play through with any non-archer (archer kind of cheats with explosive arrows now and stealth is a different style of gameplay not conducive to comparing fight flexibility/power lol)