"Considering that Fortnite is not super graphically intense" - Opinion

"The comment was just based on my experience" - Anecdotal evidence

"I have never said it is so terrible that it is unplayable," - stated it was terrible with no further validation.

"but I do expect it to run at least at a secured 30fps and with no texture loading problems affecting the gameplay." - made up baseline benchmark to prove your own argument.

"having millions of people play it does not excuse the game from criticism" - calling something terrible is not constructive criticism.

"Popularity =/= perfection" - Dismissive of others experience with the game. As mentioned many people do not have the issues you are seeing, or don't feel it impairs their enjoyment of the game.