The R-27R is simulated very well range-wise.
Both videos show an rmax of 10-16km. Of course, the aircraft (especially the mig29) were traveling at a slow speed and lower altitude, but its comparable to what we get get in DCS. Another proof are german MiG-29 pilots (there is an interview on youtube with one of them aswell) described the R-27R as a low range, relaively useless weapon.
Now why does the R-27R and T suck so hard? Well, when they were developed, most fights still happened WVR due to IFF limitations. So it just made sense to focus on superiour maneuvarability and the R-73 missile.
Why do the russians use them in syria? Because due tp many countries aircraft operating over syria, the ROE are most likely limited in a way that makes long range missiles useless. Russia is not interested in shooting down an israeli or US aircraft by accident, and will most likely require pilots to visually confirm the targets before even THINKING about weapon use. So if all (possible) fights are limited to visual range anyway, why not just take only short range weapons anyway?
If you are still in doubt, google the ethopian-eritrean war. Out of many air to air kills and launched R-27s, the R27 is only known to have hit a single mig29. Rest of the kills were made with the R-73.
PS: Regarding missiles in DCS and why the mighty AMRAAM seems to be useless above 10 miles, remember that a missile with rMax of 50 miles doesnt actually travel 50 miles. It gets launched at mach 1.5 on an aircraft traveling towards the missile at mach 1.5. It also explains why the SLAMRAAM (Aim120) SAM variant has such a low range.