If only those that adhere to Bible Scripture were to observe the phrase "by their fruits he shall know them".
I would also suggest that many use and abuse this verse, leave out a key part of the context of it and use it as a sad effort of a weapon.
Christianity has adopted some strong qualities of tribalism over time, both against the denominations within
Christianity and other religions which profess ways to God not under a specified name dictated by an apostle 1900 odd years ago.
Following you above quote in Matt 7:24 we enter a relevant part of the context of your reference and if this part was taken on board, what people seem to think and class as the fruits, would undoubtedly follow.
Matt 7:24-25 - Therefore whosoever heareth these sayings of mine, and doeth them, I will liken him unto a wise man, which built his house upon a rock:
And the rain descended, and the floods came, and the winds blew, and beat upon that house; and it fell not: for it was founded upon a rock.
That ONE Rock is now Jesus. 1 Cor 10:4
So a Key or probably the most important one in you reference is The Rock = Spirit of Truth which is the Almighty God and Father of Jesus.
Eternal life depends on knowing the True God and WHOM he sent. John 17:3.
John 4:24 - Spirit God is and those worshiping him should worship in Spirit and Truth. (There is but one Spirit in this regards here = His Spirit must be none other than the Holy Spirit and not an idol as in a god the holy spirit).
In the passage you quote, Jesus talks about the gate being narrow and FEW find it = Truth, and the untruths appear to have started around 1-150 years after Jesus and continue bu most.
They say it was only around 150 years after the flood that the truths started vanishing, Bible truths, history repeats, appears well on target.
Two Rev references as I see it and despite what many claim, only wash their robes, given white robes AFTER they come out of the tribulation.
White robes are truth.