IHT is flawed and a blunt tool, but it is the least unfair tax.
What a person leaves when they die is leftover wealth. They didn’t need it to exist day to day, they weren’t calling on it to meet the leccy bill. It’s all the money and property they accumulated in life that’s left over when they are dead.
Of that, some (a tiny 4% of estates) leave a significant amount behind. It’s entirely reasonable to divide that up between the society that allowed them to financially prosper and those members of the family and friends the deceased would like to give things to.
No one succeeds on their own efforts alone. Society gave them an education, health care, legal system, security services, local and national government structures to oversee that, infrastructure making their life possible, etc etc (damn, I am channeling What The Romans Did For Us)
All of those things are extremely expensive. If part of that is funded by the wealth accumulated by people who did well (I.e. that 4%) after their need for the money is over (because they are dead) - that sounds an excellent way to pay for it.
And yes, I will be a beneficiary of an inheritance that will probably pay inheritance tax. And no, I don’t mind because I did not earn that money to begin with.
My parents’ hard work and astonishing good luck in housing prices does not equal MY entitlement to free money.