Looks cool but seems like it's aimed at mobile and not websites? Also, how do they differ from Firebase? My previous experience with Firebase makes me hesitant

Looks cool but seems like it's aimed at mobile and not websites? Also, how do they differ from Firebase? My previous experience with Firebase makes me hesitant to use a BaaS. It works great for simple stuff but as soon as you want more control it becomes a mess compared to just having your own server. It might just be me who haven't wrapped my head around the mindset correctly though.