I am not a Delphi programmer, but I I got an old Delphi 7 application that I need to fix and it is using ADO.
The database table (MS Accesss) contains +100,000 rows and
I have found ADO + Access w/Delphi to be painfully slow, for lots of things (big table reads like you're describing, but also inserts as well, etc). My answer became "Quit using ADO and Access altogether."
Never did understand why it performed so poorly, especially when earlier technologies seemed not to.