We shouldn't exclude the entire category of questions; although they sometimes lean on the edge of being opinion-based, they don't have to be bad.
Some of them are good
I would say that Suggested order to watch entire Dr. Who? is an example of a good suggested-order question1. The OP defines very clearly what they want out of an answer (emphasis mine):
what is the best approach to continuity (an episode E1 that helps understand something in episode E2 should be watched in E1=>E2 order)
the least amount of spoilers (ala "I don't want to find out Vader is Luke's father before watching the prequels")
extra weight given to the order recommended specifically by creative team(s) associated with the show.
With the possible exception of the first one (though I think it could be worded differently to make it objective), all of these criteria have objective answers. The fact that my answer focuses on general concepts rather than a specific list of episodes should be taken as a testament to the scale of Doctor Who, not a commentary on the question.
Some of them are not
In contrast, What episodes of Doctor Who should I watch first? is not a good suggested-order question; the OP specifically says what they're looking for:
Where would you recommend starting and what are the definitive episodes/seasons I should watch?
Which is practically the definition of "Primarily Opinion-Based"; that this question has 15 answers (5 visible only to 10k+ users), many of which include some variation on the phrase "I think", demonstrates the problem
To paraphrase a much better writer than I: objective and subjective have not changed since yesterday, nor are they one thing among suggested-order and another among other tags.
If a question is asking for some objective criteria, as in my first example, then that sounds like a fine question to me; if they aren't, then they should be closed as appropriate.
1 Disclaimer: I have the top-voted, accepted (also, only) answer on this question