I don't think these apps were ever built to be fast, they were built with the resource constraints of the time. Moore's law is what's making these apps fast.
This is even more sad with Apple. My M1 Mac felt incredibly snappy with Big Sur, but is getting ever so slightly slower with each update. My iPhone SE2 is a complete disaster.
They used no networking services either. Now, I open a shared PowerPoint and am stuck waiting for a couple of minutes while it is syncing or doing who knows what. People have no sense of what templates they copy from other documents causing the size of the file and load times to bloat.
Word 2000 definitely was not very quick on a contemporary office PC (Pentium II or III), though I'm pretty certain it was much, much faster than desktop O365 is on a contemporary office PC today, despite those being >100x faster. So Fermi would estimate modern office to probably require at least 1000x more resources than Office 2000.
