Most mages do not have substantial mobility in their kit, and several solo lane mages do not even have that much crowd control. Ultimately yeah, it would be good for marksmen to be functional in solo lanes if/when they're no longer part of a mandatory duo bot lane, but that doesn't need to happen purely by giving them dashes or oodles of self-peel. As several patch cycles since the past season have shown, marksmen can become successful, even dominant in solo lanes, simply by receiving better access to damage early on. Range is a clear advantage in lane, and marksmen are a class built on exploiting theirs.
I also seriously dislike the OP because of how it frames people advocating greater team comp diversity, and more diversity in the bot lane specifically, as "ADC haters". I personally have some issues with marksmen as a class and as individual champions, but I also want them to thrive, because they're a part of this game and, despite the problems they may sometimes cause (but then again, what hasn't been a problem one time or another in this game?), have contributed positively overall. Looking at this from another angle, the current bot lane meta kind of hurts marksmen in a way, because it has caused them to be balanced around being babysat throughout the entire early game, which can often end up stripping them of a lot of agency, and limiting their laning options in a way classes like, say, fighters and assassins don't deal with as regularly. Finding a healthy way for them to more consistently lane solo or jungle, while also unlocking bot lane to other classes in their stead, could benefit them, and the game as a whole, in the long run.