His dad bought him a seat in F1 when he hadn't even raced in F2. He had 2 good performances in his first 2 seasons and then his dad bought him an F1 team and got him promoted into Ocon's seat, forcing Esteban out of F1 for a year. He scored less than half Perez's points last season, and less than half of Ocon's points from the previous year when Perez only scored 10 fewer points with Stroll as his team-mate. This year he has blown several chances at a win whilst Perez has been imperious all season, and yet it's he who keeps his seat whilst Vettel ousts Perez when the latter two should be team-mates. Perez has a race win and over 50 more points despite having a race less and even Hulkenberg was quicker than Stroll in the weekend they were able to race (a technical issue meaning he had to make an extra stop) and he'd barely been in the car.
Stroll also undermines his rare bouts of raw pace with careless mistakes, needless and dangerous collisions with other drivers and an underlying entitlement and arrogance that isn't backed up with performances. He has been thumped by Perez, he was beaten by an aging Massa who was dragged out of retirement by Rosberg retiring and the odd podium doesn't cover up for that. Even today he was ahead of Perez, made a mistake and let him through and spent most of the race behind Ocon when Perez dealt with him within 5 corners. Like Albon he's just a cuckoo and he's been shown up.