Why can I no longer use servers?

Since the 1.15 update I can no longer join servers in normal Minecraft

and I tried it with all the servers.

if I try it says connection refused and no furthur info.

Can someone help me please.

You have to set up an extra profile for each version of Minecraft with the corresponding version. No version is backwards compatible from 1.12, only playable with the current version, unless the server uses viaversion. No idea if they have already updated.