The worst bikes in TT in my opinion were those MX-bikes, I'm not a big fan in general of that genre, but my main objection is the fact there were no off-road tracks in TT to make the most of them and have some fun.
They were quite pointless on those road tracks, at least those scooters were designed for the road and although also not very enjoyable to me, they at least made more sense than those MX-bikes.
Not saying those bikes should be excluded btw, just add some off-road tracks to fully exploit their potential.