That is true. People play the 2005 ruleset in a new 2020 way. That doesn’t mean the game will be re-designed for 2020 players. Nobody offered to do that. Blizzard never offered to do that. So we have 2020 players, playing a 2005 ruleset.
NOBODY has ever said that Classic cannot be “improved”. Not even Blizzard – after all, they DID improve Vanilla many, many times.
But we dot accept the unspoken claim “anything that is not perfect must be improved”. That simply is not true. Especially not Classic.
Besides, there are as many different definitions of “improved” as there are players. Even if it was a player-defined game, there would be endless debate about each change. Luckily, it is not player-defined so the debate is irrelevant.