It’s a good site, and I’ve quoted it a few times, but our resident archivist @Gary James has pointed out a few times that the City figures aren’t entirely accurate (iirc he’s contacted the site owner, but nothing changed).
As to whether any other clubs figures are entirely accurate, I don’t know.
But if you take it and understand it as a sort of average accuracy, it’s good.
This is another site https://www.worldfootball.net/competition/eng-premier-league/ which has a lot of data although it doesn't go back as far with attendances, epsecially away from the Premier League. You can navigate using the tabs at the top of the page.