If Boeing were to give up on the MAX - not getting the grounding lifted, buying back and scrapping the previously delivered MAX aircraft plus over 400 more built but undelivered MAX - the resultant total loss would be well in excess of $100 billion (USD). Even if Boeing survived such a hit (not to mention the impacted suppliers), coming with a clean sheet replacement and putting it into production would take a decade. Just financing such a new aircraft program is going to be a challenge after taking a $100+ billion hit. Boeing might even decide to concede the narrow body market and focus on wide bodies.
I doubt even the biggest Airbus fans would see granting them a virtual monopoly on the narrow body market for at least the next decade as desirable for the long term health of commercial aviation.