OP hasn't necessarily joined 2000+ channels, their company has 2000+ channels, it's a similar situation in most companies I think…
I work for a 200+ person company and we have approximately 800 channels, maybe 20% of them are work related, the remaining channels are noise. There's a channel wherein some people in the company pick up on grammatical and spelling errors of others in the company and post them for others to laugh at, there's another channel for the three people in the company that think they know latin to make the same Monty Python joke (Romani ite domum) over and over.
For the current project we're working on, we've put in a no robots rule into the channel (no Git/Jira/Travis notifications) and when one of the higher-up managers in the company decided to join the project channel and make two joke-like comments which added no value to the project, we had the project manager remove him from the channel.
Slack has over-casualised our company, for work it sometimes works well, for distractions it almost always works too well.
I'm obviously not in all those channels, more like 20-30. One issue is that channel discoverability is poor. Searching for the right channel is difficult or impossible, since search only looks at the actual name vs. also the description. So sometimes I just stay in channels so I don't forget about them or avoid spending extra effort trying to find them again. Also, grouping channels doesn't exist so you end up with a long list of channels, making it more difficult to navigate (only can split them between starred and non-starred but that's not sufficient). Another one is leaving `threads`, and cleaning up that all threads view is extremely cumbersome. There are many more issues but those are just some basic ones.
It's not all Slack's fault though, it's also partially the company's fault for trying to embrace Slack for everything.
I work for a 200+ person company and we have approximately 800 channels, maybe 20% of them are work related, the remaining channels are noise. There's a channel wherein some people in the company pick up on grammatical and spelling errors of others in the company and post them for others to laugh at, there's another channel for the three people in the company that think they know latin to make the same Monty Python joke (Romani ite domum) over and over.
For the current project we're working on, we've put in a no robots rule into the channel (no Git/Jira/Travis notifications) and when one of the higher-up managers in the company decided to join the project channel and make two joke-like comments which added no value to the project, we had the project manager remove him from the channel.
Slack has over-casualised our company, for work it sometimes works well, for distractions it almost always works too well.