And yet: my mail flow on my Mac, using the native client, is effectively unchanged for 20 years. I've changed back-ends, sure, but that's a different thing.
Whatever works for you, but I don't believe that your mail flow on the Mac is "effectively unchanged for 20 years".
Wikipedia lists many UI and functionality changes over the years for the Mail app.[1] As recently as this year, people are upset about changes in the Mail app in recent versions.[2]
And I never had to hack anything together.