DBD has a BIG Killer problem.
This is going to get broken up in to a couple main points.
TLDR: BHVR has whittled most killer games into an extremely frustrating and stressful experience, to the point its no longer fun to even win for a large number of players.
Generator Speed
Generator speed is atrociously fast for any semi competent survivor team. First chase almost always results in 3 gens lost, usually within 100 seconds of the game starting. Coupled with Deja Vu or just gen spawn knowledge and any killer not instantly recognizing their 3 gen and defending it has essentially already begun to lose. This isn't even mentioning the amount of gen speed perks and incredibly strong toolboxes survivors can bring to punish killers even faster. So don't take bad chases? Even if the killer takes a good beginning chase, sprint burst and or pre-running almost always forces the killer into eventually taking one. 3 gens lost within a minute and the controllable 3 gen spawn almost always with it. All for one hook. "But the first hook is where killer easily can snowball". This has also been made extremely difficult to do due to...
Survivor vs Killer Perks
Currently, there exists approximately 25 "second chance" perks for the survivors, with the strongest being DS, DH, StB, and Adren. These perks were implemented to help struggling survivor players extend their time in the game after making a critical error. Given to an experienced survivor/team, however, and these perks become overpowered and extremely frustrating to play against, beyond belief. A killer can take a first chase, lose 3 gens due to the incredible speed they are able to be finished at, decide to tunnel to regain some pressure, and chase for another 40 seconds, only to eat DH into DS and still end up at end game collapse with no kills, with StB finally erasing any death hook pressure. Now the killer is forced to chase survivors to the gate while they bag him for being "toxic."
Okay, this means in order to win on killer above baby MMR they have to immediately look for the 3 gen and hold it, while only prioritizing the best chases? Seems easy enough. Except survivors will instantly recognize this and counter it by rushing every other gen on the map. If the killer does decide to take a chase, the other 3 will rush the 3 gen. Either way, the killer ends up with one gen left, and 8 regression events in the best case scenario. An extremely difficult and stressful situation, where they have to somehow kill 4 survivors while also making sure the remaining survivors don't finish the gen in ~35 seconds it takes to finish the last gen. While doable, this is already a very difficult and deteriorating situation to be in. It's a damned if you do, damned if you don't scenario. Every game.
If the killer manages to play their heart out, keeping track of the 3 gen, taking only the perfect chases, and making no mechanical or gameplay mistakes, they've won the game. They outplayed the survivors who have been probably bagging, clicking, and bm'ing the whole game. What happens now?
Abandon Feature
All four survivors abandon, leaving the killer alone in a lobby with 4 bots. It feels like a slap in the face. To spend however long in game stressing out, at the mercy of the survivors, and trying to play your best, only to be left alone in a lobby having to clean up against bots. They don't have to wait to be hooked, they don't have to watch the mori, survivors can choose to leave without feeling like they lost for more than 1/2 a second. Abandoning early also allows survivors early access to the end game chat, which regularly results in them being toxic and leaving before the killer can even respond. This is the most unsatisfying game loop ever.
If the reverse happens, and the killer has entered the end game collapse without any hooks, they have to watch as survivors bag and run around them, as they wait for the killer to chase them to gate, where they proceed to either bag or slow walk their way out of the game. This is incredibly frustrating and unfair. If killer wins, it usually doesn't feel like a win, if they lose, its rubbed in their face. Why can survivors opt out of the losing experience, but the killer, who has the much more stressful and difficult role, is at the mercy of the survivors?
The abandon feature was implemented as way to stop killers from "trapping" slugged survivors, which is a good thing, but why has the same not been implemented for the reverse? The argument "slugged survivors can't do anything to effect the match anymore so its fine to allow them to abandon, but killers still have a chance" often comes up, but its just not true. Aside from just crawling out, perks like unbreakable, tenacity, boil over, power struggle, DS, etc, all give a survivor a chance at escaping, even after being slugged. It's either all okay or none of it is.
Conclusion
There are many ways the killer role has deteriorated over the numerous updated BHVR has put out, but these are the main problems that make the role extremely problematic.
Why would someone want to play a role whose sole purpose feels like being the punching bag of the other team?