The CA Spectrum web client used to be HTML based. Now the new 'webapp' appears to be nothing more than a virtualized Java instance. Why did this happen? It feels like a step backwards. Yes the java client has more features than the web client did, but a virtualized Java version is not user friendly.
The WebUI for Spectrum has moved to the Netops Performance Center (CA Performance Center the old name). This is for better workflow for troubleshooting so staff can stay in the same UI to drill down and view the performance data with the rest of the Netops platform, CAPM, NFA and ADA.
Taking the Spectrum OneClick jnlp app off your desktop and putting it as a web app does a few things. It helps customers not have to have a java client on their desktop (a long time request). When Java 11 ships with Spectrum, Java 11 does not support jnlp anymore. So the OneClick Console will still be around for PowerUsers and Admins and could consider moving your Operators to the Netops Performance Center.
Hope this helps explain to changes.