Altough OVERFOND is a word, it sounds a little old and pedantic. It’s much better to use NOT OVERLY FOND OF something: https://books.google.com/ngrams/graph?content=not+overfond+of%2C+not+overly+fond+of&year_start=1800&year_end=2008&corpus=15&smoothing=3&share=&direct_url=t1%3B%2Cnot%20overfond%20of%3B%2Cc0%3B.t1%3B%2Cnot%20overly%20fond%20of%3B%2Cc0