They switched to hardware acceleration in the last few years and they removed the toggle to disable it. It still sucks (perf & rendering issues, eg. scrollbar not updating when scrolling) and there's no way to go back to the old rendering engine unless you disable hardware acceleration on Windows as a whole. Lmao.
what kills me about things like this is if you load a 1-2 decade old version of office on a computer today, things are fast.
all they had to do was keep up with whatever features are different in excel between now and then and implement those. leaving the menus and UX mostly alone, only improving things as time went on. update the engine to do the new features, and update the UI only enough to expose the new features and make them accessible.
but no... UX people don't have jobs if they can't redesign shit for no obvious reason. PMs don't have jobs if they can't force nonsense features no one ever asked for. Developers don't have jobs if they don't aggressively chase every new fad and tool and be in a constant state of learning (and thus unlearning).