The biggest challenge to making remote workers successful is the existing company culture. If the organization has not been built with a conscious "remote-first" mindset, new remote collaborators will inevitably be excluded from necessary communications and decisions. Making a remote worker a true part of the team requires a massive culture shift if your company does not already (successfully) do distributed work.
This takes extraordinary discipline on the part of the in-office team. Fortunately, everything that's good for a remote-first culture is also just good for communication in general. A culture of documenting everything, living in public, and over-communicating is good for any company; and burning those habits into teammates levels them up for life.
I think it's even harder for companies that have open open offices or are doing Agile. Those two things usually mean the companies are explicitly stressing in-person collaboration. In-person communication isn't a bad thing by itself, but I think that explicitly valuing in-person communication ends up making remote work harder.