I want to give a quick product update on this since it has been almost 4 months since our last update for this topic. There is a lot of powerful functionality and configuration options on the issue experience. We are getting close to having almost all of the major features (e.g. watchers being shipped recently and confluence pages coming very soon! See https://confluence.atlassian.com/jiracorecloud/the-new-jira-issue-view-938040503.html for more info and to stay updated on our progress).
We are acutely aware of the fact that we do not yet support 'Tabs' within the new issue view, but more importantly, we just simply don't handle complex configurations very well in the new issue view. We hear you and agree that just putting all fields in a massive list on the right hand side is unusable. We have learned a great deal from all of you during our rollout so far and we are working towards updating the design model to support complex issue configurations with 50+ fields and multiple tabs in an enjoyable way.
I appreciate your feedback and patience as we get closer to building this feature. It is top of mind for us.
In the meantime, I just want to remind you that there is a per-user opt out option available if you go to your Personal Settings by clicking on your avatar in the bottom left of your navigation. If you scroll down, you will see a Labs section where you can toggle on/off the new issue experience until the functionality you require is built back in.
Taylor Pechacek - Jira Cloud PM