I wish the article had more detail on exactly what Timeless did. On my phone at least tapping through to the link to try Timeless shows me a Wikipedia homepage that looks pretty much exactly how I remember it being.
The rejection wasn’t bad faith… someone at Wikimedia happened to have enough taste to say no.
The most noticeable things (on desktop) are that there's a big bar stuck to the top and the body text has a maximum width.