There are ways to exchange fiat for cryptocurrency without going through a regulated business. Bisq, localcryptos, coordinating over chat and meeting up IRL.
To be more specific: They did not speak out about blocking "the country" but about closing accounts and restricting access for all Russian citizens/residents. They are, however, complying with targeted sanctions of the individuals on the sanction list.
If the scope of the OFAC sanctions forces the exchanges to start blocking Russian passport holders and/or residents, that will change, of course.
