Every company seems to share the ritual of the prioritisation session. It has a common format and a common process.
Each business head gets to voice their opinion on what's most important to them. These are dutifully collated into a master list and then a discussion takes place to rank one above the other based upon some number of criteria; typically financial, customer experience, and compliance. Finally the agreed list is circulated for action.
It's value is normally limited because importance is not a good measure for prioritisation.
Importance is a measure of emotional conviction. It is a broad term that can mean many things depending upon the subject. The importance of a programme of work is not the same thing as the importance of an immediate fix, or the importance of a process review, or the importance of addressing a particular risk. In each case the definition of the term, importance, differs and therefore it can not be used for comparison. It is accurately a measure of emotional response, but I doubt little else.
What is the alternative? Perhaps it's better to ask what's the point.
The purpose of the prioritisation session is to allocate scarce resources. Scarcity can only be resolved through a process of trade-off (this is text book economics). What complicates the task in an organisation are the differing time requirements, resource specialisations, and dependency effects.
We have a limited ability to weigh up the combination of time, resource, specialisation and dependency factors to determine how limited resources can be applied to a range of competing tasks. Our minds have to make best guess estimates and the wider the scope the greater the problem (I bet someone out there can prove this is a power law expansion).
Which drives us to smaller delivery teams to reduce the scope of the problem.
So what should the prioritisation session be?
Perhaps to set areas of focus and define the criteria for prioritisation. I doubt little more.