I feel much the same way (work at a large company). I feel like Slack is a battle royale of one person's time versus another.

- What incentive is there for anyone to ever spend a second searching for anything when they can just DM or @ me?

- The @ in a large busy channel can derail me big-time. It churns up a lot of low priority and very unrelated questions/queries. It's like someone asking me to their desk to answer a question, and then announcing to everyone on the floor that I am there to answer their questions.

- Are you providing the answers or are you the one asking them? If it's a two way street, or you are the one asking, you probably love Slack. If it's a one way street where you only provide answers/help, you feel differently

- Seems to cater to Ask Alexa, Ask Siri type mentality. Things that were once covered by process or documentation, now devolve into "ask person or channel X".

- There is often a massive imbalance between what is urgent to me, and what is urgent to the person asking me. This was always an issue to some degree, but the immediate response requirement sometimes puts me in a place where I feel like I am encouraging bad behavior by answering quickly.

- Things that are "quick questions" often require a rather lengthy answer.

- Context is often often missing. This often happens with the people that hate e-mail, love slack, and end up asking a question to me about something that exists in e-mail. I end up asking for more context and then get forwarded the e-mail where I can figure out what the person was actually answering.

- Context again, I have to change focus to see what someone is DM'ing me about. In e-mail I can quick glance to see if actually urgent or not.

- No great OOO. With e-mail, if I am away for a bit I can put an OOO with a bunch of common questions/answers. With Slack options are limited, other than letting people know I am not available and to contact someone else. Maybe bots could help, I dunno.

- People can't complete full thoughts before hitting Enter. Hi (Enter). Have a quick question (Enter). Joe contacted me(Enter) Can we set him up with X today (Enter).

- People seem to be very dense about people in different time zones compared to e-mail. Normally not an issue since I use DND on my phone, but occasionally I've accidentally logged back in off hours on mobile somehow.

- Threads vs. No Threads Warriors. "No threads" people complain about not seeing replies in threads or it slowing them down. "Threads" people complain because it becomes impossible to link to it later. I think is where you create a temporary channel to deal with it, but that's too much work for most people.

- I had someone accuse me about being set to Away for "4 days" and asking my boss where I was. I went offline on a Friday for a couple hours to meet a deadline, and then was away for meetings for a couple hours on Tuesday (Monday was a holiday for him). If he had just asked his question on Friday, it would have been answered Monday at the latest, but probably Friday. Instead I get a "wtf" because I wasn't on the precise two times he happened to look.

In general it seems like the tool is significantly worse now that it's used by the whole company. At one point it seemed to just be a replacement for e-mail dist lists, which I can understand. As usage grew it became more of a synchronous tool (demand wise).