They are subjective in the degree to which they are measurable. How would you measure how well a text editor “integrates with a programming language”? There are many ways to measure this, making any single measurement choice subjective to a degree.
First, an open-ended survey among text editor users to identify the features/requirements that matter to them.
Second, tag and categorize those responses into a standardized list of features/requirements.
Third, survey users to determine both the relative importances of those features/requirements, as well as how well each editor meets their needs for each feature/requirement. Both of these can be done using Likert scales, most commonly giving a score between 1 (does not meet needs at all) to 5 (completely meets needs), with intermediate values being "mostly doesn't", "somewhat", and "mostly". Several hundred randomly chosen survey respondents will generally give you the statistical precision you need.
Companies do this all the time. It's bread and butter for many product managers and user researchers, to justify to execs why a particular feature ought to be built rather than other ones (combined with other factors like cost, risk, strategy, etc.).
And there you have it. To answer your specific question, to measure how well a text editor integrates with a programming language, you just ask its users to rate how well it does. Since user opinion is all that matters in the end, that's the objective answer.
When it comes to products, people's average evaluation is the objective answer. Because people's evaluations are what lead to usage, purchase, subscriptions, etc. There is no other "objective" answer.
There's nothing subjective about it. What users think about your product is your product in the marketplace. That's the entire meaning of "the customer is always right".
Satisfying user demand for a capability isn't a mathematics problem where there's some independently objectively right answer.
In other words, there's no objective product goodness/badness. Only what the customer wants. In that sense, the customer (market) is always right.
Inexperienced restauranteurs often experience the same shock. You don't cook the food you want to make, or that you think people ought to eat -- you cook the food people want to eat. Otherwise you'll go out of business.
It's a bad slogan that only portrays half of the reality of the situation.