As a 45 year old I solved it by starting my own company and using that to my strength.
However I would caution against using the mcKinsey report as any kind of evidence or guide for thinking about diversity.
It's the same claims we see when it comes to gender too.
The reality is that there are no studies showing that in general companies who were not diverse and then decided to be more diverse by some of those mentioned metrics were suddenly performing better.
A much more likely interpretation is that companies who are doing well financially tend to be able to care more about ex diversity.
You could literally have a team of 20 old female/male geezers be just as diverse as a team with the most mixed combination of ages, genders and ethnic groups you could find.
What matters in my experience is what kind of diversity we are talking about and how it's used, not just whether there is diversity.
What matters is the market and that it allows for diversity itself.
You could have a team of only 20 year olds and you can have a team of +45 year olds and they would both offer something different to the market.
I don't think you even need to worry about that part to be honest.
The benefits of age are enough:
More experience, better ability in general to prioritize, focused on their work, less likely to work themselves too hard, more stability, less likely to switch jobs for the next great opportunity etc.
I left SV tech scene due to ageism, and retarded business models and joined Cannabis Tech Industry.
I am building out some serious tech-stack for managing cannabis cultivation and manufacturing.... (doesnt matter that the product is cannabis) - but this is the industry vertical that can really benefit from deeply experienced techs from SV into this space.
Basically, it works as a multiplier; in this space, one vet tech is worth 5X people for their needs. They wont hire 5X 20-somethings that only know one small portion of the stack requirements for all aspects of running a successful cannabis business, and will value those who are capable across broad reach.