Interesting
I have been on both sides of this fence.
For a while I was completely freelance and my primary client was building an 'electronics and software capability'. They had one, but it was mainly in India. They needed to build it in the UK (primarily so they could work with companies that required security clearances).
As part of that, I was the second human (well, I claim to be one, anyway) reviewer and as I have been in this business (electronics, software, FPGAs) for a long time it was fairly easy for me to figure out who was going to make the cut; one thing that put me off (and one of the client's clients) was spelling mistakes and poor grammar.
Now that may seem harsh, but the tools we have today can do spelling checks and hint at grammatical issues. Your CV is telling me a story; make it flow a bit so I can see how you have progressed, learned new things, implemented interesting (or totally uninteresting - it might well be applicable).
On the other side of the fence, I have not had to write a completely new CV for over 20 years although I have had 5 different jobs for 5 different companies in that time. I did tailor it a bit but that took pretty minimal effort. It also meant I could make sure that all my latest experience was up to date.
On ageism: yes, it exists. I have been ghosted quite a few times after recruiters / companies figured out my age but I wouldn't want to work for a company like that anyway.
To get all the keywords in, my CV is (of necessity) quite long but it gets past the keyword search for jobs I might actually be interested in.
Electronics is somewhat different to IT when it comes to recruitment, especially at senior levels.
I have seen my share of 'we only want an Oxbridge graduate' which was a warning that they weren't looking for someone with the right skills but where they got their degree. I have seen many people with advanced degrees from Ivy League colleges who had zero common sense.
As it happens, I do not have a degree, but I have done many things that the younger crowd haven't (yet) simply due to being exposed to so many technologies (I can easily read a schematic with discrete transistors such as RF detectors, for instance). I have also had a lot of opportunities to becomes more educated and better at the jobs I have done and I make sure that is clear in my CV.
In my experience, a degree is useful in many contexts, but any degree I would have done would have lost a great deal of relevance (although I like to point out to some who think only the new shiny matters that we have not yet repealed Ohm's Law).
I had a small test (just a few questions really) at the latest place that were actually reasonable considering the role I had been invited to apply for. I know that puts some people off, but it was pretty simple stuff.
Keywords are important but so is the narrative; far more important, apparently, than the 'keep your CV short' mantra at least in my experience.
I got the latest position at the age of 66, incidentally. Some places do value the experience that brings.