The main thing to remember is that “multiple pages optimized for the same keyword do not automatically lead to cannibalization, unless the search intent of these pages is the same.”
A couple of years ago, Google's John Mueller was asked on Reddit, "How does Google view keyword cannibalization?"
John's response was:
We rank content as soon as we get it. If you have a lot of pages with roughly the same content, they will compete with each other, kind of like a bunch of kids wanting to be first in line, and eventually someone else slips ahead of them . Personally, I prefer fewer strong pages than a lot of weak ones. Don't reduce the value of your site.
—John Mueller, Google
Think about it this way:
If you have two or more pages that answer exactly the same search intent, which one should rank? Which one is the most useful for users?
Chances are, you won't be able to answer these questions, because there probably isn't a right answer.
Keyword cannibalization almost always happens by mistake, when new pages are published over time without considering what already exists.
If you can't choose which page should rank, how can you expect Google to?
The real keyword cannibalization issues are that you are asking a search engine algorithm to choose which page to rank.
Sometimes there are stronger ranking signals that tell Google about one page, but often this is not the case. In this case, what happens is that neither page ranks as well as it could have; the pages cannibalize each other’s ability to perform.
It is a significant problem that affects many websites and cleaning them up is a key task that should be part of your SEO strategy .
. Personally, I prefer fewer strong pages than a lot of weak ones. Don't reduce the value of your site.