Solitaire...the b737-800and 400 will have autopilot disconnect when the TOGA switch is pressed. So, yes...modern aircraft do require manual go-arounds. The 737-800 is a modern aircraft but will not do an auto go-around like the 747.
I stand corrected. Not flown the 737 but even the 747-100 did auto go-arounds so assumed that more modern aircraft would too.
Back in my box now.