https://confluence.atlassian.com/jiracorecloud/the-new-jira-issue-view-938040503.html
The new dropdown for switching the activity tabs is horrible. There are three issues with it:
1) Two mouse movements and two clicks instead of one.
2) I have a muscle memory for finding the right tab and clicking on it without needing to focus on it too much, however the content of the dropdown changes depending on which tab is active and so does the perceived position of the items requiring to always focus and search the desired item before clicking on it.
3) somebody relatively new or not much used to JIRA might not even be aware of the variety of tabs there are, not even talking about having to "discover" all those hidden features.
Hiding the very much used tabs under a dropdown is in my opinion poor design.
new:
old: