Expertise can’t be the final target.
This is only for specialists in a very restricted field.
Specialization isn’t the way for the mastering.
It’s a good point only at a low level.
Even at the intermediate level
it’s already a problem.
There are too much frictions
and they are more than the degrees of freedom.
This fact doesn’t allow an efficient evolution
and the resolution is impossible.
The mastering is beyond expertise.
And this has to be done in several fields.
Although they are different.
And this is the first step
for diversity which is essential.
If things are similar
then they are useless
for the construction of a  strategic mix.
And this synthesis is impossible
with only the tools of analysis.
Even brainpower needs sometimes serendipity
to discover a really innovative resolution.
For all those reasons, the specific skills have
to be combined in a complex way.