Thank you for the verses you quoted.
17 Even so every good tree brings forth good fruit; but a corrupt tree brings forth evil fruit.
18 A good tree cannot bring forth evil fruits, nor can a corrupt tree bring forth good fruit.
The problem, as I see it, is that everyone thinks they are partaking of good fruit. Who will be the one He tells, "I never knew you"?
There are many wonderful people out there and they all believe they are doing as God asks, including me, or at least trying very hard to. My thought is that you must study scripture and follow it to know what type of fruit you eat.
Excellent advice
All Scripture is God-breathed, and is profitable for doctrine, for reproof, for correction, for instruction in righteousness, (II Timothy 3:16)
And by this we know that we have known Him, if we keep His commandments. (I John 2:3)