Servers are not interoperable by default. There is 3rd party software that acts as a proxy letting Bedrock players connect to Java servers but it'll just remove anything that the more limited client doesn't support.
They both use completely different network stacks, Bedrock using RakNet over UDP, Java using Netty (?) over TCP, so they have to be translated accordingly.
Yes. So clearly it's not a question of being able to run, or of weird graphics quirks or something. It's a strange omission. Given that Mojang is now owned by Microsoft, it's slightly suspicious…
You can use Geyser [0] to "bridge the gap" to Bedrock clients. There are bugs here and there, but it works pretty great to get everyone on the same server.
They both use completely different network stacks, Bedrock using RakNet over UDP, Java using Netty (?) over TCP, so they have to be translated accordingly.