ClaytonCross
Kinder reader Inflection wanted
That does sound like a problem with design but of a player wanting to change characters design without changing character in the same campaign. This can be fixed with a story mission and GM letting them rebuild their character as a result of completing it.As others have said, I think this sounds a lot like 4E and i don't think wizards wants to go that direction.
I think a major problem with this is that it is difficult to make options that are good at low level and also good at high level. This means you typically have to have prerequisites, and a skill tree and it railroads your build at a very low level. I want to get feature C at 12th level so I need to take A at 4th and B at 8th because they are prerequisites to C. Once you have taken B you are locked in to C and you I can't ever take F because that requires D and E and you will never get those.
I think with Tasha's, the current system is very good at offering a mix of class features that can't be changed, subclass features that can be swapped out en masse with an entirely different subclass, and feats which are open and arbitrary.
Your argument against is MORE true in 5e than what you describe in 4e. In 5e You pick a class and your locked into a set of class features, you pick subclasses and your locked into those subclass features. This is the problem you describe magnified many times. Not only are you locked into an early level feature that prevents other options, but your locked into middle and later features you may not have even considered because you were only looking at 1st level features at character creation. The artificer and warlock however are very popular based on their drastically greater flexibility in class features because of how invocations and infusions work. I know I love them.