Chapter 2 in context:
The Colossians i.e. pagans, uncircumcised, were aliens to the faith now through the cross they are now one with the circumcised.
Do not let anyone judge you:
Here Paul didn't say the Jews i.e. circumcised but rather "anyone" so it could be
a. the Jews judge why the Colossian believers, uncircumcised, observe what they observe.
b. the Colossian pagans judge why the Colossian believers would observe the Jews' dietary laws and feasts.
Basic principles of this world:
"World" G2889 used 187 times in NT. More than half of it's usage is "anything other than the Jews". Could it be used for "Jewish traditions" or "Jewish and pagan traditions"? Do we see such clearly without prejudice in any of it's usage? Would the Jews (those who don't believe the Messiah) accept and teach the basic principles of the pagans in the synagogue when they preach circumcision?