Op, stop beating yourself up. My child was “v late” to come out of nappies, ie well past 3.
FWIW my kid is now a (ridiculously!) super brainy, very sporty, very nice teenager now. I see that he quite likes the easy life, even now (chilled out personality); so probably nappies were just easier for him, who knows. But at the time I also worried (he was also late to walk!). So I would say to you, to stop attempting this with such focus, since it’s making you doubt yourself and him. He’ll get there… (unless of course serious learning difficulties, in which case, again - it’s not his/your “fault”).
someone said to me at the time, there are no university students in nappies (unless a fetish), and that helped me put it into perspective haha.
Not sure if it’s been said on here, but we used a musical board book called “pirate Pete”, and he liked that.
but it was actually the (Gina ford inspired) offer of choc buttons that broke it when he finally stopped with nappies. But not the one button per potty, as per her advice. No, the cheeky kid (who wasn’t given chocolate at the time - yes, I was one of those parents) asked for the whole big bag, in return he said he’d stop with the nappies (!). This i did, and he was never wet again. Dry through the night too, unlike his little friend who potty trained at 2.5 but needed night nappies until at least five…. Again, I see this as part of his (perhaps hyper lazy/competent, both extremes) personality!
God, this age is tough. But they do bumble through!