Because this season only Liverpool did not have any problems with their players, if there were any absences it was only in few match and different from other team such as Manchester City and Arsenal who had to deal with problems related to player crises several times.
Even so, the Premier League remains one of the biggest and most popular league, competition like this with significant decline in team is natural thing to happen, and you are right at least in European competitions several team from the Premier League can still play well and can be said to be quite dominant for some time now.
That is the difference when several teams from England who are not good in the Premier League but can be better in other competitions such as the Europa League because there the opponents they meet are very different from the opponents here in the Premier League. This season Liverpool is indeed much stronger than other teams and also much luckier than all other teams so that Liverpool's level of consistency has not faded until now. Meanwhile, for Manchester City and Arsenal, they are only fighting to survive in the UCL zone this season because it is no longer possible to catch up with Liverpool at the top of the standings.