Given that, the acetic acid won't all dissociate and it will exist in equilibrium. This is what causes the H3O content to be less and therefore less acidic?
Have I covered what was wrong with my first stab at an answer?
Yes, this part is correct, and well explained. But ...
Ok, so far i've figured out that after the H+ dissociates from the CH3COO-, the CH3COO- becomes a conjugate base and the H3O+ that is created becomes a conjugate acid of the former H2O.
This is technically correct, but all acids dissociate into their conjugate base and a proton, this explanation of yours doesn't really have a bearing on the question at hand. Likewise, from before ...
Since HCl is monoprotic,
... is perfectly correct ...
it dissociates completely
Likewise correct, but your word "meaning" here ruins everything, because it is not the reason, or the actual definition of the terms.
Sometimes, I see a beginning chemistry student jumble random text from their book together like this, so I want to tell you to be more careful. Chemistry doesn't follow English grammar rules -- just because two statements are physically close to one another in a text, doesn't mean they can be combined any old way.