Again, I don't see how the translation/interpretation of τῶν ἀγγέλων changes any implications for our understanding of 2:16-18. Even "messengers" could be used to describe spirit beings rather than human prophets (Ps. 103:20; 2 Pet. 2:11). We must also think about the context in which 2:18 was written and what necessitated its composition. In other words, what is the Sitz-im-Leben for the verse?
2:16 is fairly specific when it maintains what Christians should reject. The dietary laws of Lev. 11 seem to be encompassed along with Jewish festivals like new moon and the Sabbath. Historically, keeping the Sabbath has been an identifying marker for reverent Jews (Exodus 31:14-17). Furthermore, according to the Tanakh, Sabbath was only given to Israel--not to Gentiles.
I also keep asking myself, why observe dietary laws for devotional reasons if Christ died for my sins and I'm now justified by exercising faith in his shed blood? What religious purpose would keeping dietary laws serve?
From Coffman's Commentary on Col. 2:16:
All of these refer to Jewish observances; as Macknight said, "Some of these were enjoined in the Law, and others by private authority." Of particular importance is the appearance of the sabbath commandment in this list. "Although the article the is not in the Greek, it clarifies the meaning; Paul was resisting the Judaizers who insisted on legalistic sabbath observance." As F. F. Bruce expressed it, "It is as plain as may well be that Paul is warning his readers against those who were trying to impose the observance of the Jewish sabbath upon them." The sabbath observance is here placed upon the same footing as the other things abolished, and "Thus Paul commits himself to the principle that a Christian is not to be censured for its non-observance."