This is 100% incorrect and not what fair use means, ask a lawyer.
> We will still insert the license going forward as it makes it more simpler and straightforward.
It's also legally required, and for many licenses (most CC licenses) you not only need to somehow include the license but also attribution.
I know very well how CC works, and if you would please read the link you yourself posted, you will understand that the way you are using these images clearly does not fall under fair use, as a compilation/library of anything whether that's images or songs or movies or whatever is not "news reporting, teaching, [or] parody" -- what these examples all have in common is that you're creating a derivative work ON TOP of the original work, which is why it's "fair use".
e.g. https://uploads-ssl.webflow.com/5fba626e86ad1be131127616/5fc... on https://www.vektors.pro/illustration-packs/b-w-illustrations
Maybe it could be argued that this is fair use, but why not just go the extra mile and do it properly?
> We try to keep the license info as simple and accurate as possible.
If the licensing information was "simple and accurate" there wouldn't be an issue. It's missing, misleading or incorrect in many cases.
And on the subject of content removal, this is from https://www.vektors.pro/privacy-policy
> If you find any link on our Website that is offensive for any reason, you are free to contact and inform us any moment. We will consider requests to remove links, but we are not obligated to or so or to respond to you directly.
How are creators supposed to contact you? There are no "proper" contact details in the header, footer, terms and conditions or privacy policy, just a Twitter link.