An ELO of 1200 is mediocre in FIDE or USCF rated chess. Check the Classic Chess leaderboards for CM Live. A few have figured out how to boost themselves into grandmaster territory, 2500-2800. In other words, 1200 is nowhere near the potential maximum.
The problem is the bar for beginning players got set too low at 600 ELO. Presently, the pool of players rated over 1200 is very small. It's just going to take time to increase the numbers who have reached that level. But if you keep playing, sooner or later you'll get a chance to beat a few of them and that's how you get yourself to 1200.
I don't deny it's difficult at the moment. Maybe Ubisoft needs to patch the ELO calculations to give more of a boost for winning until the whole population is raised to a level where the CM Live ELO rankings equate more closely to FIDE/USCF. But given how long it took just to get the no-move cheat fixed, don't think we'll ever see anything.
Personally, it doesn't bother me. If it's a concern for you, pick up the rest of the achievements first and then getting screwed out of your potential 200 will carry more weight.