Point: There are microtransactions in Dead Space 3, where the player can buy in-game resources for real money. Those resources can then be turned into weapons and armour. The alternative way to get weapons and armour in-game is to find it / grind out the resources to make it and there are some pre-made DLC weapon and armour options for purchase (11 all up according to that source).
Adding microtransaction-based DLC to Dead Space 3 is seen to be a negative because it reduces the feel of the title as ‘survival horror’ – you can buy your way into being more powerful, which is against the spirit of the franchise. It also violates the internal logic of the Dead Space world – you’re no longer strapped for resources if you can pay for them with real money.

And if we are talking about consistent in-game logic, we can’t forget that the most powerful weapon in Dead Space 2 is the Big Foam Finger.
Counterpoint: Here’s a list of all the purchasable DLC weapons and armour available in Dead Space. There were apparently 12 different DLC packs.
Here’s a list of all the purchasable DLC weapons and armour available in Dead Space 2. There were only four DLC packs (excluding the extra narrative of the two Severed levels) but they were more fleshed out than for the original Dead Space.
Dead Space and paid DLC have a long, long history. Adding in a button directly into the store is somewhat new, but the overall concept – spend real money, buy virtual things – has been tied to the Dead Space franchise almost from day 1. Getting bent out of shape about it now seems a bit short-sighted in view of that history.
As for the internal logic of Dead Space, it’s always been video game logic. You have to suspend a lot of disbelief to accept the world (which is good, because I sure as hell don’t want the dead coming back to life looking extra angry / ugly being something that’s believable!). For instance, necromorphs can drop circuit boards on death that you can sell back to the store for money. That only makes sense if you accept video game “dead enemies drop valuable items we can sell for cash” mechanics.
Engineer and Unluckiest Man in the Galaxy Isaac Clarke also buys his ammunition from vending machines, including ‘ammunition’ to equipment that should be his day-to-day tools (the Plasma Cutter, Line Gun, Disc Ripper, etc) along side military grade weapons (the Pulse Rifle). The ‘engineering equipment’ makes great weapons to kill necromorphs, but would be lousy in any kind of construction situation – do engineers really need timed mines for building purposes? It’s a future apparently shaped by both Ayn Rand and the NRA (“Electrophied javelin guns and flamethrowers don’t kill people – people kill people. The Founding Fathers would have wanted Pulse Rifles to be sold in vending machines too.”).
Oh, and if you buy a new space suit from the store, you then climb inside the vending machine and it it changes your clothes. No normal clothes are available even in the very metropolitan setting of The Sprawl (for Dead Space 2), just space suits, weapons and ammunition. Vending machines OF THE FUTURE, I guess.
Finally, and most importantly, you don’t need to spend money on any of these things to play and enjoy the Dead Space franchise. Buying these DLC packs will make your life easier and / or make Unluckiest Man In The Galaxy Isaac Clarke look a bit cooler, but you can earn everything you need in-game.
You can disagree with microtransactions and DLC weapons packs being available in-game at all, but to date a lot of the negative commentary thrown at Dead Space 3 seems to be aimed more at giving EA a kicking than considering the issue in context of what’s happened with the rest of the series.