This is a case of a "sticking qualifier". The statement is a general statement, an overly basic sentence. Includes affection, with a specific word as the qualifier (love). Might even be a verb, as basic sentence composition would dictate.
In this case, the person loves dogs in general, but might not like x or y, or most. "Dogs" in this sentence is a singular object of affection, the plural form of the word dog.
Thus, there is no qualifier, but a sticking feeling thanks to generalizing.
Akin to saying: I do things.
No, there is no qualifier there, implied or otherwise. One might try to play with undertones, or sarcasm, which would carry extra info, but since these are just characters on a screen, i don't hear it.
It is valid, but instead of a qualifier, there is a missing sentence fragment. "I love dogs, in general./mostly"
"Does lack of a quantifier imply a universal quantifier?"
Depends on personal preference. Generally speaking, assume most.