Why can't Britain assimilate Ireland in history?

We understand the relationship between Britain and Ireland from three aspects:

1, Irish ancestors are Celts and English ancestors are Anglo-Saxons. In terms of blood relationship, Irish and Celtic are closer.

2. In history, the British occupied Ireland, and Ireland suffered from British colonial rule for this reason, and finally could not bear to leave Britain.

3. In order to change the ethnic composition of the island, the British moved a large number of immigrants to the nearest northeast region of Britain, which changed the ethnic composition of this region and made Northern Ireland stay in Britain after Ireland's independence, which became one of the two major reasons for tension.

From a historical and geographical point of view, the close relationship between Ireland and Britain is mainly due to geographical factors, which makes them neighbors. However, Ireland can't compare with her big brother Britain. After all, Britain is an old colonial power, and it is not easy for Ireland to catch up with Britain.

However, Ireland is not decadent, but has embarked on a unique road by its own efforts and is known as the "Silicon Valley of Europe".

Except for some special reasons, Ireland and Britain are constantly entangled, but the relationship is still very close. After all, there are too many similarities on the surface.