What to do with a water damaged iPhone and a terrible support from service center

I had my iPhone 11Pro and my iPhone 7(work phone) together in my pocket of a rainproof jacket and doing a short hike under the rain and my iPhone 11Pro got water damaged meanwhile iPhone 7 is working perfectly, zippers were closed, occasionally I took out both phones to check signal, direction or took few pictures and put back into pockets. Rereading the water proof or repellent specification of iPhone 11Pro which have a rating of IP68 under IEC standard 60529 (maximum depth of 4 meters up to 30 minutes) and considering the usage which damage happened and specification I am sure there is a design issue with the unit, I really don't see any other explanation. But just left the Apple store in Ginza Tokyo and service wanted to replace it with an hefty additional cost. I am very unsatisfied with the build quality of this phone and two years ago had the similar issue with my iPhone X, it feels that I am getting ripped off all the time by Apple. Even the Apple Center supervisor Ryan (forgot his surname, but he should be the supervisor of a technician named Jun) said himself he doesn't have much confidence in build quality of the iPhone. Hearing this and still Apple asking me pay money for a replacement for a phone that been bought less than 2 years ago left me speechless, considering my previous experience with iPhone X. Right now I am without my personal phone just before my flight on birthday.