What is exactly fantastic about that?
It uses the same UI framework as the rest of Win11 (finally), the wide structure works a lot better than the small, tight one, it natively allows dragging items to reorder them, and just looks overall cleaner and fits better. In the current iteration of it, it has a border which technically matches the start menu, but not the taskbar. This would just be an optional toggle to "use native Win11 system tray," so those that want to keep it can. If you need more convincing, check the Win11 subreddit and articles online. The majority agrees in that the new system tray looks really good.
So disable StartAllBack taskbar altogether, why mix old and new?
I downloaded your software because I liked how it changed some stuff, such as the taskbar and the start menu. Why mix old and new? Because some of the new is good, but not all of it; and some of the old is good, but not all of it. It would be the best of both worlds, and it would be an optional toggle. If you want your software to get more users and more purchases, it's wise to appeal to the largest audience possible and listen to requests that actively make your software more accessible and customisable.
I guess you're right.