Most here are detractors of investing in Digital currencies. Recently, many institutions and large corporations are making forays into the space. Why is there still so much skepticism then?

This is new and highly volatile.

you could get rich or loose everything.

then there are already many competitors.

and is it said that it is bad for the world climate...

One big one: The tools to value crypto currently aren't as developed as those to analyse, say, equities.
I would say though, the folks who believed in crypto years ago, are the ones who really invested despite the huge scepticism. It really isn't so bad now.