Too big to fail? Just an example, like our local banks, singtel or ascendas reit. Since the probability is low, is it worth it to invest in these companies rather than a etf which has a lower yield?

Too big to fail? Yes. But they may stay at the low price for a prolonged period or worst case forever. So it is better than going to zero but still a big loss if this happen.

We cannot take things for granted. Too big to fail might happen to us in Singapore. This explains why we always need to diversify our investments, so in the event if one of those stocks fail, you do not lose everything.

With, only for example, the current corona situation we see what can evolve (Sasseur) from single equity investing.

ETFs seem the better diversified, lower risk option (VNQ, S-REIT ETFs could be successful)

Buy a basket of these companies, best of both worlds :)