That's strange, I've tried it on low-end hardware too and so far, no other players haven't reported issues. For now could you try downloading the windows build?
I believe it may be because itch isn't able to run the web version of the game over slow/unstable internet. Maybe try again at some other time?
It is also a known issue with the web build that sometimes refreshing and running it again can make it smoother or have less lag(I suspect this is because webgl tries to load too much at once). Please give this a try and let me know how it goes!