Not only is Schick an important player in the Leverkusen squad but Xabi Alonso has built this team quite evenly in all lines even though Schick often becomes Leverkusen's savior with the goal contributions he creates.
Leverkusen is actually still at the same level but Xabi Alonso's cool hand can change everything with the tactics he applies which can create a team performance that is quite strong and consistent.
Yes, Xabi Alonso's cool hand is indeed unquestionable, which has a big influence on Leverkusen's success in competing in the Bundesliga in the last two years. Xabi Alonso with a squad that could be said to be mediocre became extraordinary because he played solidly and strongly. Xabi Alonso is also smart in building relationships while in the dressing room, so it is not surprising that Real Madrid is interested in him and with a heavy heart Alonso accepted the offer.
For next season Leverkusen also has the same level of players and the same team finances, so I doubt a little that Ten Hag can concoct the same strategy as Xabi Alonso to maintain the team's performance.
Erik ten hag is actually a potential coach, this was also seen when he previously coached man united, because for me seeing a man united coach is indeed a bit difficult because coaching man united is very difficult because it has complex problems. Now it is different coaching Leverkusen which of course does not have the pressure that man united has. Therefore, I am sure that in the hands of erik ten hag, leverkusen will remain consistent and be able to compete with bayern munich. However, I also doubt Erik ten hag to get a trophy because this is his first season.