Is it okay to mix formula into puree? Why or why not? Thanks!

I feel it's best to intro pure taste of the fruits, veggy to the baby 1st and see their reaction. You don't want baby to relay on the milk taste too much also right. That every meal also need milk right. Sometimes maybe baby don't like apple but like pear? Don't like carrot but like avocado? I have friend's kid who love to eat celery, which i don't like