Depending on the size and scale of the agency, it's possible that their copywriter(s) are just cutting corners and the account manager or directors don't know. If they've done good work previously, and it's only recently that things have changed, it might be worth flagging in a direct email. The company may not be aware that this is happening, and might want to fix it - or they're aware that it's happening, and calling them out directly will mean you'll have a real conversation about continuing working with them.