I mean, it's at least popular enough to get it's own genre tag, even though it's technically a sub genre of romance. No other sub genre in romance or any other section has gotten that. (and keep in mind that not all BL uses the BL genre, because it's both a new tag and BL can also be cross genre with another, as well as not all BL has the BL letters in the corner of it's icon)
I think usually when people mention it, they talk about it in tapastic's 'popular' algorithm. Usually the series that show up there are either premium, or BL. BL the most popular genre readers look for outside of the premium titles.
And yeah, BL does get traction on this site, I have a friend that has his comic uploaded twice, one with a BL icon and one without (there is no BL in the comic) and the comic without the BL icon has something like 100 subs while the one with the BL icon has 1500 (despite it having no BL in the comic) He doesn't update his comic anymore due to real life obligations, but his 'BL' series still keeps growing in subs.
Outside of tapastic community, the actual tapastic site is more known for it's BL or uncensored BL by webcomic reading communities. It's a popular go to for that specific content. Need some free BL webcomics? Tapas is a common recommendation that will pop up in both fujoshi and LGBTQ circles.
I have the BL tag on my comic even though it used to be in the drama tag. It just performs a LOT better on this site even though the main focus of my comic is not the m/m relationships, it's more of a side plot / that's just how the main character swings thing. I consider it more of a LGBTQ comic is anything, as the relationships are there but aren't highly sensationalized / sexualized / fetishized. Also, the tag was more a suggestion from my readers who kept asking when and if I was going to put the BL tag/warning on (I DO NOT like the idea of BL being a 'warning'). Though before that I've also has readers that have clicked on my icon thinking it's BL (it's two guys in the icon) only to drop comments such as "I thought this was just gonna be just BL but it has a story and it's so much more I didn't expect this OMG"
Is it being popular a bad thing? No, I don't think so. But it IS a thing, and there really isn't anything wrong with that.