Unfortunately, I'm coming to realize what you say is true. Now that I think about it, there is NO issue that negatively affects my work/life balance more than having Slack installed on my phone.
If you strictly limit notifications it's okay. I'm fine with being notified of a critical bug or problem when I'm at home, and happy to grab my laptop to help. Even if sometimes it turns out to not be so critical or important.
But if you, unlike me, actually have hobbies or planned activities for your free time, deleting might be better.
There is a poison dart in your phone, a la. Raiders of the Lost Arc. Every time you open the slack app, there is a 1 in 10^16 chance of that arrow shooting out and killing you. I think it's in the speaker grill and it usually points downward, if you know what I mean.