this ones a common question but the answer tends to come back to a lot of the usual "just keep posting" and "get yourself out there" advice. regardless of whether you're posting a comic or novel gaining views and subs or getting interactions is always a tough thing to keep consistent and kind of has been for a while
when it comes to visibility people often recommend paying attention to where and how you market your work. things like your target demographic or at the least the kinds of folks you think would be interested in your work. what labels you use, that being genre tags and other descriptive labels for your work kind of like seo [search engine optimization] stuff that would get your comic in this instance to show up. and then from there is just promoting in as many places as possible to get eyes on your work whether that's the forums, social media, conventions etc. again tho that still falls into a lot of the kind of bare bones core advice that's often given since just about everything else is played up to chance and how consistent you are with keeping at it.
knowing your target demographic makes it easier to know who to advertise to and where to go to find those people (sometimes) but it's still no guarantee those people become subscribers and they could still be reading the work even if they're not subscribed. i'm one of these people when it comes to certain comics i've read on other sites especially when you think about self hosted comics. search engine optimization stuff when it comes to tags is useful because it can sometimes make your work easier to find so if you've got a fantasy story for example getting a bit more specific with your tags can help with the reach bit there.
but all said reminders do also help at the end. yeah there's the whole it seeming tacky coz it's basically the text version of the ol youtube "like comment subscribe and hit that bell" but like do what you gotta do, no shame in it. plus at some point when the discussion was more prevalent i guess people did notice folks sometimes liked an episode more often than not if there was a little reminder to at the end of an episode. it's why i did them for a while when i was actively posting comics. dunno if i'd bother with it now but it is an available option
all said it's very rarely got to do with the quality of your work (at least in some cases) but reader behavior varies a lot both depending on what platforms they're reading on (being mobile or web) but also just heir own personal habits. so some may sub to keep on top of every episode as soon as it's out, some are bingers that let episodes pile up and then read in bursts, then you get folks who come in maybe dig the comic but maybe dont feel inclined to sub but maybe come back to it later or maybe not at all but still give it a read. it's...an unpredictable and absolutely impossible thing to control but you do what you can to nudge readers in a certain direction and whether they follow or not is still ultimately up to them. best of luck tho and keep at it 
