Perhaps there were some misunderstandings: (some things might have changed since I last signed up for Slack, so bear that in mind)
You can't sign in to your account without first joining a channel (perhaps there's a way?)
The wording is confusing. Channels are conversations between (mostly multiple) people within Teams. I don't know if you misused the term here or I didn't catch the meaning. You don't sign up for "Channels", you sign up for Teams (within these Teams you can manage Channels). These Teams are completely separate and you don't share any information between them, other than that you can use the clients to sign in to those Teams simultaneously and switch between them whenever you choose.
This is understandable. I can't remember that happening to me, but having these e-mail notifications as an opt-in rather than an opt-out made always more sense to me.
I don't really agree with this point. It's really subjective (and it seems you got off on the wrong foot and try to justify disliking it with a rather broad statement). There's certainly a lot more going on than there was at the start, but I only use a tiny portion of the interface (be it mobile or desktop) and found that the rest doesn't get much in the way and is really easy to use once you get to it. But as I said: pretty subjective.
This goes with Point 1: you sign up for Teams separately and of course when you install the client you have to add them one by one (in case you confused Channels with Teams).
Perhaps there were some misunderstandings: (some things might have changed since I last signed up for Slack, so bear that in mind)
The wording is confusing. Channels are conversations between (mostly multiple) people within Teams. I don't know if you misused the term here or I didn't catch the meaning. You don't sign up for "Channels", you sign up for Teams (within these Teams you can manage Channels). These Teams are completely separate and you don't share any information between them, other than that you can use the clients to sign in to those Teams simultaneously and switch between them whenever you choose.
This is understandable. I can't remember that happening to me, but having these e-mail notifications as an opt-in rather than an opt-out made always more sense to me.
I don't really agree with this point. It's really subjective (and it seems you got off on the wrong foot and try to justify disliking it with a rather broad statement). There's certainly a lot more going on than there was at the start, but I only use a tiny portion of the interface (be it mobile or desktop) and found that the rest doesn't get much in the way and is really easy to use once you get to it. But as I said: pretty subjective.
This goes with Point 1: you sign up for Teams separately and of course when you install the client you have to add them one by one (in case you confused Channels with Teams).