The way I look at it, people who don't personally do it themselves are either
A) missing out on a whole new experience or
B) feel what they already do is an accomplishment in itself so trying to justify something new as being less or as difficult is not worth understanding.
I've been drawing my comic series for well over 5 years now and working on a new one starting later this year and it is a lot of work and commitment, keeping consistent (as humanely possible) update, constantly trying to improve, keeping track of subjects I've already made strips on, and getting kicked to the curb once or twice by some of the nicest comments I can get (which unfortunately I still have to take with a grain of salt). Not to say artists and writers don't have their own ass smacks they need to put up with, but what they usually think of when they see webcomic is: oh you mean a four panel slice of life that talks about "relateable" humor, cause honestly it's those same artists that claim webcomics are easy that produce those kinds of comics.
Yes being an artist is hard especially if you rely on it for your source of income, but claiming comics are just illustrations combined is vague, it's also a HUGE commitment. At least with an artist you're not forced to draw the same characters all the time without getting burnt out, you're allowed to branch out and take on unique commissions and jobs that can change things up (unless you're hired to work on something then $&%* you get back to work and stop making petty complaints, I'm only kidding). Most times whenever an artist starts a webcomic they're usually pretty quick to give up on it when things don't go their way, I've unsubbed my share of comics because of that mindset, hell I'm friends with one who tried to make a comic cause of it, he's so damn good at art, but could not deal with making comics. I can't vouch for writers, I don't know any who don't already make a comic, I know you have your struggles too, I imagine mostly involving spell check or something jk.
I wouldn't get too perturbed about the comment though, you can be that one voice that shines some enlightenment into their heads.
Just remember to enjoy what you enjoy