I've gone through https://community.fandom.com/wiki/User_blog:Kirkburn/How_images_are_picked_to_represent_articles thoroughly, and found nothing helpful to get a specific image I'm using on a page to become the thumbnail, following this, I tried to find people with my same problem to see what their solutions were. Most, if not all, discussions I've seen on the topic of the wrong images being autoselected as a page's thumbnail, have had no solution, since shortly after the person is linked the article to how images are picked end in no response from the OP. I can't assume whether or not it solved their problems and what they did to solve them, so that did also not help.
I don't understand why the only way to choose a page's thumbnail is through randomized image selection. This is a faulty, unorganized, useless system, that usually has no way of specific targeting, unless you removed every single image from a page, including templates, galleries, slideshows and anything with a PNG file, and left only the one you wanted to be put as the thumbnail matching the satisfaction criteria. In fact, in some cases, even with the criteria being matched with only one image in the page, the autoselection process will sometimes still only take a text quote from the page.
The thumbnail autoselector can be useful for those new to editing wikia pages, who don't know how to go further into the details of editing and formats. But for an organized wikia with many experienced editors, autoselection is a buggy burden that is both hard to satisfy and sometimes, even when the criteria are matched, will divert from it's wide range and pick something that it shouldn't have according to the selection rules.
This is why we're in need of a setting that allows us to either check an image to be ignored from selection (such as those in templates), or specifically tag a picture in an article's gallery, slideshow, or sliders to be selected as the thumbnail by default.