In 2018-19 all four EPL teams advanced to the group stage. 2 teams played in the Championship match.
Europa was an all EPL final as well.
In 2019-20 all four EPL teams have advanced to the group stage. Both EPL teams won there group in Europa.
Don't confuse parity with mediocrity. EPL may lack two dominant teams like they had last year, but the results in Europe suggest that the league far from mediocre.
And if I had to guess why the EPL is struggling to find another dominant team, I'd say that star players don't want to have to scratch and claw just to play in the Champions League. If I'm a European star, it's certainly not lost on me that UCL finalist Tottenham was one draw away from spending some cold winter days in the far reaches of the continental shelf. Guys like Eriksen and Alexis aren't leaving the EPL for tougher competition that's for sure.
Minor Nit - 7 EPL Teams Still in European Competitions