The real power is in Number 10, not Buck House. There is no big popular movement to make the UK a Republic. It was tried once in England and it didn't end well.
The Heritage Foundation's virtual event is a) a waste of time, bandwidth, and speech.. and b) based on a flawed understanding of the British monarchy. The left can't cancel the monarchy. As long as Elizabeth and her successors act in the way that Elizabeth acts now in running The Firm the majority of the UK population will continue to accept the Crown. Yes I know there is a Republican movement in the UK but it really is in the minority.
The concept of the Crown solves some problems that are inherently problematic with a Republic because the government and civil service are loyal to an apolitical body called the "Crown" that's led by an apolitical king or queen which has no true political power. A lot of Republics have people who are loyal to a president - who is political and wields actual power. One could argue that the UK is a Republic except that instead of an elected president that the UK has an unelected head of state but essentially the UK works like any other Republic.
One also has to think that Canada, Australia and New Zealand could have gotten rid of the UK monarchy as being their head of state ages ago... but to this day Elizabeth is still their head of state. I wouldn't be surprised to see in the future that Canada, Australia and New Zealand do become Republics in the end but the Republican mechanisms that replace the Crown will be modeled after the Crown and have a President who would wield little to no power.