Concratiulations Microsoft, once more you managed to keep my entire company from doing our own core business for an hour or so, by not only introducing a new feature, but also rolling it out set as enabled without even asking the tenant admin for permission. This Wild West attitude towards customers may be usual in America, but here in Western Europe this is perceived as rude and brutal.
Apart from that, without this app launcher sidebar we were already in short of horizontal space in Outlook even on 1920 x 1080 p screens. So we disabled it and we don't want that to be temporary as stated in the 2211 update notes above.
The first 6-7 years or so, Office 365 has been a great asset to this company, but the last few years it has become more of a burden than help. Disabling stuff that we don't need and did not ask for has become a monthly task.