Not sure about that. People played 4-4-2 for fifty years. It had been figured out long before that. There's no secret about defending with men behind the ball, and hitting teams on the break. It's hardly a new thing. More problematic is teams knowing that we don't necessarily conform to the modern convention of not putting the ball at risk. What's your thinking, try not to defend as well, try not to attack quickly?
Loss of Elanga's pace and strength will be more problematic than 'being found out'. We need to be better on the ball, so we aren't defending it so much. Ultimately we had a season where things went as well they could defensively, and also attacking. We are unlikely to get the same conversion rates and keep the same lid on goals conceded. Not because we've been found out particularly, but because of a reversion to the mean.
