Logic: Baseboard has existed for 50 years. If baseboard could not replace radiators, the first heating units – bulky radiators – would be the only ones that exist. Conclusion: Yes, baseboard has replaced radiators.
Additional info: Baseboard is not so good as bulky radiators for steam heat systems, so if you tell someone that you have a steam system they would recommend bulky radiators.
If you tell people that you have hot water heat, they might recommend radiators (espscially in GB), baseboard (especially in the US), or floor radiant heat (especially in continental Europe.)
“The symptom of dysfunction is the creation of secrets.”