Is having a light workload also a blessing?

Working only 2 hours a day, with the rest of the time being personal time.
Guaranteed retirement and a seniority-based pay system.
It was great when I first joined.
But now, seeing peers building their careers and growing,
I feel like I'm falling behind, so I'm considering changing jobs.
Others tell me I'm being ungrateful and that I should use my spare time to study or invest,
but what do you all think?