I’ve never had much luck with WINE, but every now and then I give it a go. This ultimately leads to failure and disappointment, and I really don’t know what I’m doing wrong. That being said, when I saw ‘Play on Linux’ in the boutique, I got excited. Since it was in the boutique, I made the assumption that it would just work as apparently, it passed muster to appear as an option. I soon learned that there was an issue. When I installed ‘Play on Linux’ I made the assumption that it would set everything up for me. Though, when I launched it, it gave me a message indicating that WINE was not installed. When I went to look for WINE in the boutique, it was not there. If the market/target audience for Ubuntu MATE is the novice user, should the expectation be for them to go through the pain of installing and configuring WINE before installing ‘Play on Linux’, or should MATE recognize that it is not installed and take the necessary steps for them?
I know that ‘Play on Linux’ is not a priority, but If we want to bring people to Linux from Windows, should items like this be a consideration?
PlayOnLinux is more of a front-end to manage Wine. By default, it'll use the system installation of Wine, but it's not an absolute requirement since PlayOnLinux can install releases of Wine. Their idea of having different Wine versions is that some programs may work better under older versions of Wine.
If you'd like the latest release of Wine, the WineHQ team themselves have an official PPA for Ubuntu which you can install:
Historically, the Boutique did have Wine listed on its own... they will have been a reason why it was removed. I think at the time, there wasn't an official Wine repository, but there was an unofficial "Ubuntu" PPA that was unmaintained for a long time. Another issue is that you could install Wine on its own, but it's not obvious how it's used as it's not shown in the application menu.
There is a wine package in the Ubuntu repositories (outside of Boutique), which can be installed using one of the software managers listed under Boutique's More Software category. Unfortunately, that particular package ends up a few versions behind.
Sounds more like an objective for a Linux distribution like Zorin OS. Ubuntu MATE has a different set of objectives with a different solution to a mission (preserving and modernising the traditional Linux desktop).
In my view, Ubuntu MATE has its signature Welcome program to inform new users, rather then promote compatibility with Windows software. Compromises may need to be made; alternate software to be found; and Wine is good at crossing the bridge. As you've pointed out, we can improve this experience and expectation in the Boutique.