I finally have a bit of time to look at touchpad pointer acceleration in libinput. But when I did, I found a great total of 5 bugs across freedesktop.org and Red Hat's bugzilla, despite this being the first thing anyone brings up whenever libinput is mentioned. 5 bugs - that's not much to work on. Note that over time there were also a lot of bugs where pointer acceleration was fixed once the touchpad's axis ranges were corrected which usually is a two-liner for the udev hwdb.
Anyway, point of this post: if you're still having issues with pointer acceleration on your touchpad in libinput, please file a bug against libinput and make it block the new tracker bug 98535. The libinput documentation has instructions on how to report a touchpad bug, but amongst the various things I need is your laptop model name.
Don't complain about it on reddit, phoronix, HN, or in some random forum, because you're just wasting bytes there and it won't get fixed that way.