UI/UX review and recommendations

We have a software product that is now 7 years old and needs a UI/UX review. Features are being continually added and extended and as a result the UX has evolved rather than being thought through holistically from the start. It's not always intuitive for a user how things work. The psychology of user interfaces has also moved on a lot and there is an opportunity include the latest thinking on how to make software more fun/rewarding to use (animations, rewarding popups etc.). We would like to get to the point where the software is positively a joy to use

The primary goal of improving the UI is to increase user adoption. This would be measured in three ways (in order of importance):
1. Faster growth of the user base within existing customers
2. Feedback from existing users that the software is easier to use vs competitors
3. Better conversion of sales leads

The product is deployed within Atlassian Confluence when a customer wants it to be fully user configurable. We have limited control over the UI of confluence but can write Themes. Obviously we have a lot of control over our add-ins. Attached are a few of screenshots - the 3rd screenshot shows the list of components that need to be assessed. The first screenshot is of a Chart, the second is of a KPI.

There is a lot to it and the intention is to do this in two stages:
1. An initial review and recommendations (this project)
2. UI mockups and web design library for the agreed way forward

The scope of this project is:
- review the existing software and identify a prioritised list of improvements that need to be made
- put together examples of how it could/should be (anything - sketches, mockups, pintrest board - just to convey ideas)
- present a report of recommendations and scope of next phase with estimate of effort required