Our satellites these days provide data that substitute for RAOBs. This isn't low res stuff either. You also have aircraft reports etc to help. Besides, we aren't trying to decipher things like timing a s/w to induce cyclogenesis off the east coast. We are looking at a broad area to analyze things like outgoing long wave radiation, 850mb winds etc. We then use guidance to see how this will propagate. They'll be some errors for sure, but you aren't going to see gross errors in the MJO 1-2 weeks out.
FWIW those RMM plots are noisy and typically not the most accurate.