i never said push ups don't benefit you in any way, simply that they do not compare to free weights. you will eventually hit a limit of gains from doing purely bodyweight exercises, to get stronger you have to continually increase the workload (this means weight/repetitons/speed of repeitions) increasing the number of repetitons increases strength only to a slight amount (anything after about 12 reps is going to be pretty much all muscular endurance), increasing the weight is what really makes you stronger hence the need use free weights.
now using yourself as an example of gaining strength from push ups is fine, and though i don't know your personal circumstances i would presume (and by all means correct me if i'm wrong) that you maybe haven't trained with bodyweight exercises for very long/a very regular basis (having a long break from doing bodyweight exercises then going back to them will once again increase your potential gains) allowing you to get a benefit from them.
i have a lil bit of an exercise obsession :
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