Different weapons do different things. A charge blade, while damaging, can't KO, or apply statuses well. Also, they have a fair amount of downtime between their harder-hitting attacks, so other weapons with better sustained damage can catch up.
At the very least, every weapon type is almost certainly usable to solo everything at the game, if you're good enough.
Impact Charge Blades and Hammers literally exist to KO monsters. The CB can even KO monsters just by guarding. And they can apply statuses just fine. A Nerscylla sleep CB can sleep a G-rank Diablos in a few attacks. It's no different from a sleep greatsword. The problem with the status CBs is that they do significantly less damage.
The CB's weaknesses are:
1. Slow moving. Axe form is ridiculously slow moving.
2. Sheath time is long.
3. You can't cancel most attacks, especially big ones, leaving you open a lot.
4. Sharpness decreases like mad.
5. It's not a beginner-friendly weapon.
6. Very short range and most axe attacks have limited attacking arcs, making it easy to miss even stationary targets.
7. Elemental CB requires very good accuracy to be better than Impact.
8. There's too few choices of CB, making upgrades hard.
9. If you mess up your combo, you will spend an inordinate amount of time finishing off animations, making your DPS crap.
Honestly the biggest weakness of the CB is how hard it is to learn to use. I mean, look at this shit:
https://www.youtube.com/watch?v=KxzwD4XnXRA&feature=youtu.beHowever, it makes up for this complicated nature by being super duper strong.