Unsolicited advice can sometimes be taken as criticism or distrust. “I can take over from here” can sometimes be received as ‘they don’t think I am doing a good enough job’. It’s important to be aware of this when offering your help.
Of course, at the same time, an important part of a marriage is that you support each other.
When offering to help, express it in a loving way that connotes that you are available to support them as they want, that they don’t need to do it alone if they don’t want to. “I’m here for you. Let me know if I can help.”