You're right, and i think there are more to blame such as Henry Ireton for the brutality caused in Ireland but lets not downplay the brutality of Cromwell.

The 1640s campaign was the latest in a 100 year campaign of genocide of Irish culture and people that expands beyond arguments of contemporary tactics.

The Tudor reconquest had a particular aim to destroy Gaelic culture, outlined in great detail in works by Lord Camden and Edmund Spencer, including tactics of scorched earth and how best to kill an displace Irish from the land. This ending in the flight of the earls was the major hammer blow tpogaelic civilisation.

Its was still surviving afterwards for the following years but Cromwell firmly put the secular gaelic order in its grave. By the time of William of Oranges wars a few decades late all that was left was its religious distinction until the gaelic revival of the late 19th century.

So in relation to destroying Irish heritage Cromwell was by no means the only the only vicious agent of it, but was undoubtedly the head of the most brutal. It just theres more blame to go around