There won't be more timewasting since the 5 subs have to be made at 3 different moments instead of 5, so the amount of subs taking place will not be more.
Also disagree that it favours richer clubs. What it would do for Liverpool for example is that it would give more opportunities to the likes of Harvey Elliott, Curtis Jones and Neco Williams in games where we have a big lead. In close games or important games, it won't make that much of a difference. A fourth and fifth substitution will always lead to a decrease of quality, apart from City who have an out of this world bench. You're not convincing me that our fourth or fifth sub, whoever it may be, is an upgrade over Sadio Mane who's just played 80 minutes. They're professional athletes.