I'm not sure what you're talking about… the fact that plugin managers continue to be developed for Vim and Neovim tells us there are new use cases today that didn't exist 20 years ago. Neovim isn't your undergraduate Vi/Vim from back in the day.
What's amazing is the plugin managers continue to improve, especially for Neovim.
Lazy.vim [1] is amazingly good.
Refactoring eliminated 30% of Vim's legacy code and the choice of Lua for the scripting language has unleashed a stunning amount of creativity in Neovim/Vim community.
https://github.com/folke/lazy.nvim is maybe a more interesting link
For me, Neovim has always been faster than VS Code and that was before switching to Lazy plugin manager.
On vim, I was using vim-plug, which works fine with neovim too.
At some point I switched to Packer, which is written in Lua and is definitely more powerful. Now I would recommend Lazy instead: https://github.com/folke/lazy.nvim
Yes, it's silly that neovim still doesn't come with built-in plugin management. Installing a plugin should require 0 lines of config.