Long time lurker and I have to say that I wholeheartedly agree. Lots of people who argue for BIONICLE's return act like LEGO is obligated to keep the theme active or alive when really the way it is structured just wouldn't work in the current climate, LEGO is a much different company now than they were when BIONICLE was running, and it's such a harder sell in modern times. BIONICLE's original marketing was a product of its time, the internet was still fairly new so utilizing things like the MNOG and websites to discover more about its world was more exciting, but like I said that was 20 years ago.
Now, BIONICLE still does have an active fandom and it DOES get referenced from time to time, but honestly that's about as far as it goes. It is certainly a niche with a dedicated following, and occasionally on places like twitter and other social media I'll see people mention that "they should bring bionicles back" and the like. Now we definitely don't need it back as was previously stated, I've moved onto other hobbies and if LEGO never makes another BIONICLE product again I wont be too phased, I'm too old to care that much and a lot of other fans are as well. However I do occasionally get nostalgic and think about how that could be done and honestly? The only conceivable way I could think of is just make it a D2C theme comprised of pricier, more detailed remakes of older sets aimed specifically at fans (though they'd probably mostly utilize system parts and I know that would be polarizing to fans, but with all the system mecha and stuff I personally don't think it makes much of a difference.) They could release one or two initially to see how well they perform and release a couple figures at a time every few months or so like most premium figure lines (think of how SHF releases figures if that makes any sense.)
One of the main reasons why G2 even happened was because of fan demand, but BIONICLE cannot work as an evergreen theme anymore. However if there's still a following big enough that's interested in buying new product I feel like this would just be the best course of action. That way the expectations for sales aren't that high and it'd be an easier sell. After all, BIONICLE won the 90th anniversary fan vote twice, so there is a clear demand of some kind. It isn't gargantuan or anything but there's a clear handful of AFOL BIONICLE fans that would probably throw money at something like that. And if the first one or two figures were to underperform, then that's that.
Sorry for the long first post lol, and if I'm wrong about anything here please feel free to correct me or counter if anything I've said here sounds too outlandish. Again, not saying the theme NEEDS to come back cause it certainly doesn't, plus the amount of fan content like the games, fics, and MOCS are proof enough that LEGO isn't needed to keep this series alive, but when I hear people talk about how new "official" stuff could be made most of the time it just doesn't make any sense (i.e. another reboot in the form of a G3)