Libreelec is not an embedded system, and "we" can take advantage of that fact
I've quoted the "we" for emphasis ^
Kodi devs made a serious proof-of-concept for a Kodi-internal browser 3-4 years ago. This proved that it was a non-trivial feature to bring to Kodi. The prototyping showed a mountain of platform-specific code was needed (Kodi supports 6+ platforms) and it would also need frequent updates to manage the inherent security issues of a browser; the underlying browser engine (Chromium) is in a state of constant change for the same reason. The team concluded that adding a browser is technically possible, and we all see the value of having one, particularly to ease the challenge of accessing streaming platforms. However the overall level of effort required to implement and then maintain an in-Kodi browser doesn't align with how Kodi is [under]staffed since forever or the anarchic way the project operates itself.
I feel a lot of hostility towards actual users when they have reasonable requests like this.
I'm normally aiming for sarcasm more than hostility, but "we" get bored of new users showing up and expecting us to treat their reasonable suggestion differently to all the previous times the same reasonable suggestion was already reasonably answered.