On May 25th, 2018 the General Data Protection Regulation (GDPR), a new European data protection regulation, will go into effect. Unfortunately, in order to comply with this regulation, we will remove the Monobook skin from our network as it is not possible to bring it into compliance.
We understand that this is a drastic step and is an inconvenience for you and your community but we must be in compliance with this new regulation. For more information about the GDPR, please see https://www.eugdpr.org/gdpr-faqs.html"
Yeah, I saw... I'm super bummed about it, both because I really don't like the Oasis skin and because I've been doing so much work to support both layouts recently. I'm not sure why Monobook is even an issue, either. I'm familiar with the new law and I don't see why a skin would cause issues (it's all about requiring sites to make user data portable and erasable, which has very little to do with the front-end).
I was hoping to create a Monobook-like replacement skin - I'm really not a fan of the Wikia/Oasis skin for this site - but it looks like having multiple Wikia-style skins is no longer an option.
I read through all of their forum posts on Community Central, as it seems there was a demand for clarification on this, and it sounds like Monobook collects user data in a certain way which may not be compliant. In order to prevent ambiguity, and because they don't have the resources to allocate to making the necessary modifications, they've decided to kill it altogether.
One thing is that it sounds like this was met with significant resistance within the FANDOM organisation, as they have said the late-notification of the issue was because it went 'down to the wire' as to whether it would be kept.
Currently, I'm using a global.css to hide the wikia rails to avoid all of that Fandom trash. I kept them up for ages because I wanted to be exposed to the same experience most users are, but then I started seeing spoilers on article titles within a day of ST:Discovery episodes being broadcast, so they had to go!
Anyway, here's to hoping the feedback they're receiving currently will go some way to providing a better/alternative to Oasis.