Is it worth to hold on to a perpetual endowment plan if no child to pass on to?

You could see it as another tool similar to CPF with a little more liquidity and flexibility to withdraw in total on a future date.

While CPF is great, the rules aren't in your control. So with your current policy at least you get to choose when you want the money or just continue to let it compound.

Passing it to a child is only a secondary benefit and it doesn't have to be the main consideration as you can still benefit from it within your lifetime.

Fundamental approach is to challenge your initial motivations for the policy. In their absence, check if there is any other purpose for it (retirement, etc). If it has lost its purpose and has no other utility, consider the risk-reward of keeping it versus stopping it.

If you want to sell your policy, you can always try second hand policy brokers like Endowment Exchange and PolicyWoke.