Wouldn't that mean they had 6 months worth of enjoyable gametime, though? Which would kind of suggest that it was not a boring and defective game? Those who indeed do "realize" it is boring after 6 months can go back to Retail or some other game/hobby and continue having enjoyable time. And those who apparently did not "realize" it, can continue enjoying Classic for years to come. Seems like a win-win for everyone to me. ^^
Edit: JFYI, I love both Retail and Classic but if I have to choose which one to spend my time on (and I kinda have to due to limited time), I would have to go with BFA (and any further expansion). Though I love the idea that if I ever have downtime in BFA/Shadowlands/++ I can just enjoy some time in Classic as well until a new content update. Seems like the perfect balance to me, I just cannot comprehend why both sides (Classic vs Retail) are so bitter at each other when happiness is right there in the balance between both.