My ds1 is exactly like yours. It's been almost a year of toilet training and at 3.4 years it's still wet pants multiple times a day.
Sometimes we get completely dry days but never more than 3 in a row.
We make him put his wet things in the washing machine, use praise and chocolate rewards for each wee but they stop working after three days. He stops caring about them.
He's stubborn about sitting on the potty or toilet, will insist he won't do a wee, proper shouting that he doesn't need to, but then will wet himself not three minutes later.
To the poster above smug about potty training all dgc before 2, well bully for you. I did all of the above and am still stuck here one year later. No one needs to hear how easy it was for you. OP (and I) need to hear about how others cracked a challenging case. Rest assured we did all the usual stuff to no avail.
In our case we bought pants he likes (and he will always choose pants over nappies) and he sees all family members use toilet. I also always explicitly tell him I'm going for a wee if I need to leave him so he understands we all interrupt our activities to go.
We praise wees highly, both prompted ones and especially those rare unprompted ones.
Accidents are met with a sigh, we ask him why he didn't use the potty. 'Wees go in the potty' (for the eleventy millionth time) and ask him to put his wet things in the washing machine.
Chocolate rewards work but never for more than 3 days.
We started to put him in a nappy if he had an accident and will earn his pants back if he wees in the potty next time. That also only worjs occasionally.
We sometimes get dry days at nursery and sometimes numerous accidents.
Poos are 99% reliable so I wonder whether he either has urge incontinence or can't always feel it. But he obviously does know what urge feels like as we sometimes get three days of perfection.
I share your frustration OP. I'm so envious of those whose dc potty trained with ease.