Leverkusen was a name of terror for all teams in the Bundesliga last season. No one expected Leverkusen to perform so well all of a sudden. Another big reason why Leverkusen did so well last season was that the big teams didn't have much of a plan for this team. However, with the performance of this team last season, each team planned separately against Leverkusen, which resulted in this team losing one match at the beginning of the season.
I said last season that Leverkusen won't be able to perform as well as they are doing in the Bundesliga this season, and I've been putting Bayan Munich ahead ever since. But I must agree with what you said, any big team can be beaten by Leverkusen so every big team has to be careful and make no mistakes especially Bayern Munich if they want to win the Bundesliga title next season.
Leverkusen were the Bundesliga champions last season so they were used as a reference or benchmark for other teams when they wanted to improve and rise so from what we saw last weekend when Leverkusen was defeated by Leipzig is proof that the team has been able to make changes to cover this season while Leverkusen as a whole did not make many changes so their quality tends to be the same as last season.
However, regarding the strength or the most respected or wary team in the Bundesliga this season, Leverkusen is still one of them and they are even favored to defend the title this season and for Bayern or Dortmund are teams that are in the process of improving so that all possibilities are still possible to happen.
The point is that the competition for the Bundesliga title this season is likely to be fiercer than last season, I think it will be better and more interesting.
Although Leverkusen lost early in the season, I believe this team will stay in the title fight until the end. Leverkusen and Dortmund could cause problems for Bayan Munich this season, although they have the potential to be better. Every team left Leverkusen out of the plan last season and Leverkusen took advantage of that opportunity to go undefeated last season and secure the title. After each team played two matches in the Bundesliga, Bayern Munich is number two in the points table, Leipzig is third and Dortmund is fourth.
I did not discuss the team that is in the first position because this team will not be consistent and will be defeated by the big teams.