I think the disagreement is with this claim from the article (2nd to last paragraph):

Sci-Hub, more so than RG, therefore seems to have a greater potential for disrupting the current order of things and poses a significant threat to publishers and librarians, who cling to the mistaken belief that the key to Sci-Hub’s success is its alleged seamlessness (a single sign-on), which if they can replicate will go away.

The author is arguing that seamlessness is not Sci-Hub's only advantage versus traditional channels, but that "Much of the growth of Sci-Hub is therefore ideological", "publishers are seen as the enemy, whose greediness erects unnecessary barriers, thereby obstructing the advancement of science" and that "Sci-Hub is seen as a ‘Robin Hood’ figure"

Ah, I see. However, I understood OP's primary reason for preferring Sci-Hub to be the one that he iterated in their first paragraph: "Nevertheless, I prefer this platform because I disagree with the publishing model of most publishers...."

That seemed to agree with the bulk of the article, even if they also liked the UX better. The article doesn't say it isn't better, it just says that the UX isn't the primary reason most researchers are using it. That seems to jive with OP.

Just for your reference: compliments

Complement means when two things go well together.

OP used “complement” correctly - as in, ease of use complements (goes well with) scihub being free.

OP was replying to someone who said they disagreed with the article, and argued that scihub was easy to use. OP said the article praised scihub’s ease of use, meaning complimented it.