It's not just English league teams that are counted as strong teams in the Champions League, But teams from Serie A and also Laliga and the Bundesliga will be included in it. Barcelona, Real Madrid, Manchester United and Manchester City as well Bayern Munich and Psg still have the same opportunities and all teams will show their best strength in the grub phase later.
Are you just calling teams that have history to be considered as the big teams in this years tournament. Teams like Manchester united aren't meant to be included as top teams as they have no chance of winning this year champions league tophy, they probably might get kicked out of the competition in the group stage as they have always been getting knockout of recent. Manchester united making top 4 finish in their local league this season is going to be a big achievement as the top 4 position (fighting for a champion league spot next season) is looking more challenging each season. Barcelona, PSG etc aren't no big teams anymore, Barcelona has been awful in the champions league even though they have been phenomenal in the league games and PSG has lost Neymar and Messi, only Mbappe can't do the job.
The truth is that Pep Guardiola has been one of the best managers of his generation and there's no way that we can talk about European football managers in the history of the beautiful game of soccer that he won't be named among the elites.
His ability to continuously rotate his squad and play his players in their strange positions and bring out the best in them is also another reason why he's regarded as best among all the active managers in football
Pep Guardiola changed the game of football, before managers wanted typical sticker as they thought they can't win games or trophy without having one in their team but Pep Guardiola showed everyone that it can be down and he did it multiple times then also signed a striker and use him to win the treble. Pep Guardiola is a genuine Manager excluding the fact that he can't manage a team that don't have cash to spend. Also there was a school of thought that supported using same lineup week in and out to increase the chances of winning the league but Pep Guardiola has rotated the whole thought as having squad depth that can be rotated is now been sorted after instead of relying on same players every week.