What’s a good phrase or id­iom sim­i­lar to "go­ing in blind" or "jump­ing in the deep end"?

Solution 1:

A few possible idioms that come to mind are:

"Rushing in where angels fear to tread" (line from Alexander Pope, leaving implicit that the rushing is done by a fool). This seems better than "jumping in the deep end", which speaks more of courage than clueless bravado. https://en.wikipedia.org/wiki/Fools_rush_in_where_angels_fear_to_tread

"Like a bull in a china store", implying a total and inexcusable lack of awareness.

"All guts and no brains", similar to the first one. This would be a play on the idiom "All brawn and no brains" quote by JFK (which I can't find a link to, sorry).