I used to be able to run the client on Low Spec mode absolutely fine until one patch a year or two ago, even the Low Spec mode became horrendously slow. Riot says that they don't prioritize the client since it doesn't really affect the actual gameplay all that much, well it really does when despite it saying Low Spec Mode, they still need to force in the fancy sound effects as well as animations for the Runes during champion select. Why? If it was proper Low Spec mode I'd expect to have no animations so the gameplay is ACTUALLY unaffected. As last pick, if I had to pick a counter to their (just before) last pick, choosing a champion and setting up runes on the fly is absolutely impossible.
Frequent freezing of animations make it impossible to "click early" on certain runes and the default setting is always set to that you can't actually click ahead unless the previous line of runes has fully loaded with all it's flashy animations and sound effects. Why is this a thing? Why wouldn't you guys at Riot want Runes, something that can literally guarantee a win or loss, so inaccessible behind "appearance"?
If you guys actually want to implement a proper 'Low Spec' mode or hell, even a new mode called something like 'Minimal Spec' mode, get rid of all unnecessary animations in the entire client. It doesn't matter if it looks cool or not. We get used to it and it means absolutely nothing to anyone who has used the client for more than a week.