hi anon! i definitely think that "zines" have grown in scale quite exponentially in the last maybe like, 8 years..? initially there was a bigger distinction between artbooks and zines. (i can only speak of fandom zines, and i can't speak on behalf of comic and more experimental, personal zines found at zine fairs.) i remember growing up with "artbooks" on deviantart in the early 2010s (e.g. symphonic hue, kingdom carousel) and it seemed they were more original art focused, akin to the pixiv yearly artbooks. i was starry eyed and i dreamed of joining projects like those ...
there were probably fandom based zines too, but my first exposure to them was not until a few years later, in the mid 2010s when professional book printing became more accessible + fandom projects became more popular (which i think is wonderful because anyone can make their zine dreams come true). i was definitely on the internet for a long time but i don't know the zine culture before the 2010s, but feel free to share if you were there!
the first zines i encountered on dA also didn't have merch. zines are very extravagant nowadays and sometimes i think they really should be called "artbooks", and i do like to remind people that zine projects are a business in the end, but i digress. i can also talk about my experiences working with zine projects another time.....