Google’s John Mueller said it again, if you 301 redirect pages that should 404 to your home page, Google will treat them as soft 404s anyway and thus all you are doing is confusing your end users. There is no benefit in using a 301 redirect for a page that you killed off when you are redirecting it to a page that is not relevant to that 404 page.
You should only 301 redirect pages to other pages that have a one to one relationship and not ones that are unrelated. So if you have a page about apples and you decide to get rid of it, redirecting your apple page to your home page is not useful.
John Mueller said on Twitter it is not useful to users and is treated as a 404 anyway. Here is the tweet:
Yeah, it’s not a great practice (confuses users), and we mostly treat them as 404s anyway (they’re soft-404s), so there’s no upside. It’s not critically broken/bad, but additional complexity for no good reason – make a better 404 page instead.
— 🍌 John 🍌 (@JohnMu) January 8, 2019
Forum discussion at Twitter.