You do realise how old the 737 is?
The 707 was geriatric when I flew to LA on one in 1983, in fact the plate in the cockpit (you could still visit back then) was marked BOAC.
737 was designed around turbojet engines, adapting it to high-bypass turbofans has always been an issue, they don't have the ground clearance.
Hence the flattened "D" on the cowls, max has the engines lifted higher and forward to make room.
Boeing have been flogging the airframe design well past its useful life; they need another failed defence contract to pay for developing another civilian airframe: like the 707 and 747 were
In the late 80's I flew Gatwick to Corfu in a Dan Air 707, it creaked all the time and was unable to land at Corfu due to light mist by the airport so we were rerouted to Athens for the day. Personally I've never been a fan of Boeing.