With all that said, should it still be a factor to look at when investing in ICO?
It doesn't matter that there are ICO rating sites which you can bribe(what site was that btw?) in order to obtain a better rating. The good news is that there are many ICO rating sites and when considering investing in an ICO you have to check out all of them. Even ratings on sh*tty sites can provide some valuable information for you. For example, if an ICO has unimpressive ratings on most trustworthy sites and, at the same time, has top ratings on sites like you've mentioned, it means they bribed the site which makes them even less trustworthy.
Also, you can look for an info on ICO rating sites here on bitcointalk. For example in this https://bitcointalksearch.org/topic/the-top-4-most-reliable-ico-rating-websites-2913032 or in similar threads.
What is definitely a wrong thing to do is ignoring ICO rating sites while researching on an ICO.