The JCE editor is still available, but they plan to phase that out soon too, since that editor predates any modern and maintained WYSIWYG editor out there now. The editor used to write articles now is called TinyMCE, which gets amazing community support, and all of the features and improvements added to Joomla 4 will make sure the wiki won't need a big update again for a while.
If retro is what y'all miss, I can possibly look into dumbing down the theme a bit so that it matches the old look? Although, the nav menu under the logo could use some condensing if it's a bit too long to scroll down from, probably some sub-nav menus could do it some wonders.
@Nevermind ultimately makes the calls and I simply do the tech-related work for him so that the wiki lives vulnerability-free for the most part and up to date whenever it's due for an upgrade.