Might be a dumb question, but is Credit Karma's ratings/suggestions actually helpful or just marketing tools?

I have 3 active credit cards (no balance), a 799 score, and paid-off car (1) and students loans (3). No late payments or delinquencies. Credit Karma is suggesting that I have too few accounts (7) with too low of an average age (5.5 years at the moment).

Is this something I should be concerned about seeking to improve, especially if I am considering purchasing a home within the next 5 years?

I have seen churning suggested, but it's not something I have much interest in, both because I don't feel that I need a new card and because the time required seems excessive given the return.