Metrics

I dislike using any metric related to StoryPoints, since it actively disconnects a team from the Market and from the end-users.

That disconnect is positively dangerous because it conditions everybody’s mind to celebrate the Effort, rather than celebrating the Outcome. 

What is the right metric for Outcome?

(1)
Needless to say, the audited balance sheet is the best Metric for Outcomes.  

But for that one needs to wait till the end of the financial year, it is a long time. Actually too long to take any meaningful corrective action.

(2)
The second best option can be the Metric that represents "Value shipped" per Week/per Month/per Quarter or whatever. 

Typical resistance/reluctance from a team to any metric related to Value is, that it is difficult to measure Value. Which is kind of true. 

But that can not be a good reason to settle for a metric that indicates nothing but Effort, like Velocity. 

That would be like saying... since it is difficult to obtain protein, let us settle for carbohydrates alone.

The effort is (mainly) an educated guess by the Engineers, and the Value is (mainly) an educated guess by the Product Owner. 
Both are educated guesses.
A metric related to Value_added_to_Product is worth tracking.  
When a team thinks about the Value of a piece of work, they can start thinking about the RoI of their work. And in turn, it leads to prioritizing their work based on RoI. 
A team can not do that unless it is an outward-focused team.

(3)
It is also of utmost importance to use Voice-of-Customer as a metric, which helps the team to validate the ‘Educated Guess’ made by the PO about the Value.

VoC Feedback helps the team to understand what is the "Market Perception" about the Value they have shipped. 

VoC also nudges the team to do the Course Correction as & when required, as quickly as required. 

Interviewing users is extremely useful to understand Usage Experience, Ease of Use, etc.
But a well-designed product with good Instrumentation Code built into the product itself delivers tons of Usage Data to the Product Managers & Dev Team w/o asking a single question to the end users. This is a very powerful way to gather invaluable & unbiased usage data.
A well-designed product also (often) means that it is built with Feature Toggle capability. That would help the team to do A/B Testing quickly and gather VoC Feedback accurately.  

Metrics that indicate Value and VoC, nudge the team to be more & more outward-focused. And a team can not be "a"gile unless being outward focused. 

I am talking about "a"gile , not "A"gile.

To be "A"gile, there are lots of certifications available from multiple vendors of the Agile Industrial Complex.