I've always loved the Royal family and have a lot of respect for the Queen but yes I do think it should now end after the Queen.
And this, in a nutshell, is the problem with the argument the OP has put forward, and that I’ve seen many others put forward on MN over the years. ‘I like the Queen, but maybe after she dies...?’ is not an effective or relevant argument. I’m not a Republican, but I do fully understand the arguments in favour of it. And if you seriously believe in the idea of a republic, ‘Let’s just let it happen when the nice old lady we all like dies’ is not the angle to take.
The entire basis of the monarchy - the basis on which most republicans object to it - is that it’s a hereditary form of power/privilege. It’s not Big Brother or Strictly Come Dancing; you can’t just vote out the ones you don’t like, or keep pressing redial for the ones you want to make the final. The entire concept is that the eldest child or closest living heir of the current monarch succeeds them when they die. There’s no job interview, public vote or suitably test. If you want a republic, you should want it now, regardless of who is on the throne. The monarchy isn’t the Queen, or Charles, or William - it’s the institution. THAT’S what you’re for or against.
Apart from anything else, ‘Scrap it when the Queen dies’ is laughable from a practical point of view. The Queen could die tomorrow, or she could live to be 110. Do we start planning now, or do we wait for her to die and start the morning of the funeral? Because it will take a huge amount of planning. Look at the mess that was Brexit - and that was after only 50 years. Try to imagine unpicking a constitutional system that’s been in place for centuries, and which also affects the government of several other nations. If we’re not even going to look at it until the Queen dies, we could easily have ten or fifteen years of King Charles. Also, what if she outlives him? What if the people who want to base the system on whether or not they like who’s in charge say, ‘Oh well, we quite like William, and the kids seem sweet...’ Do we scrap any planning for a republic and go back to square one?
If you’re in favour of a republic, fine - argue for it. But come up with an argument and a plan that doesn’t ignore the entire premise of the monarchy.