@Michael-Young ,
You do what’s best for you. If you’re looking for a graphical file-comparison environment, I like the one that comes bundled in TortoiseSVN. And when I’m on linux, or a Windows machine that has gvim installed, gvimdiff is great (if you like the vim-style editing)
However, I must contradict your factually-incorrect statement: Compare Plugin 2.0.1 runs just fine with Notepad++ v8.1.1 (the most recent): my version that I upgraded the Notepad++ with Compare Plugin already installed continued to work without difficulty; further, I just made a fresh unzip of Notepad++ v8.1.1-64bit portable, and used Plugins > Plugins Admin to install a copy of Compare Plugin v2.0.1, and it installed just fine, and works just fine. So to claim that “the compare plugin which no longer installs” is factually incorrect. There might be some combination of circumstances in which there are difficulties, but since you didn’t provide any version information, or otherwise ask us to help you debug your problem, but instead obviously came here to vent, there’s not much likelihood that you’re willing to ask for help.
For others reading this, who might not be as annoyed as @Michael-Young, but are still interested in why “nobody tested the compare plugin”: For Notepad++, the Plugin development is a separate process from the Application development, so it is not up to the Notepad++ application developers to test to make sure that all plugins are compatible with the most recent Notepad++. Instead, it is up to the individual Plugin developers to keep up with Notepad++. And for the Compare Plugin, the developer has specifically stated that the plugin as it currently exists will no longer be updated, but that he is working (albeit slowly) on a new ComparePlus plugin, which will have more features and will include everything needed to match with the new toolbar icon requirements for plugins.