When I open the "Edit" link for a page in a new tab (in the background), the 2017 wikitext editor doesn't load until I switch to that tab. After switching to the tab, the editor takes another second or two to load, with the progress bar shown. Ideally, the editor should load in the background when it is opened in a new background tab, so users don't have to wait those extra seconds when they switch to the tab.
Topic on 2017 wikitext editor/Feedback
Sadly this is a decision made by your browser, and we can do nothing about it.
Assuming you are using Chrome, more information can be found here: https://developers.google.com/web/updates/2017/03/background_tabs, including instructions on how to disable this for yourself with a flag.
Thank you for the explanation!