"fast" probably depends where you're coming from. Moving to Alacritty (and then WezTerm) from iterm2 was definitely a very noticeable difference for me, and just "felt" better. Of course iterm2 isn't exactly slow, but that feeling of UI immediacy in faster terminals does help me focus on the task at hand. If your existing terminal is fast enough to not notice, I suspect you've already hit the point of diminishing returns.