No, there is no age at which you'd be exempt from attending Mass. That's sort of like saying is there an age when you're exempt from spending time with your spouse, or exempt from eating.
Attending Mass should not be viewed as an onerous obligation but as a life-sustaining encounter with the Creator of the Universe, as a privileged visit with Christ, our Bridegroom.
Of course, anyone, of any age, who is sick or infirm, or taking care of those who are (or even taking care of young children), need not attend Mass. This is a judgment call.
The closure of Catholic Churches due to the SARS-CoV-19 virus is governed by each diocese individually. There is no global (yes/no) answer.
Consult your diocese's web page or contact your parish.