its not some conspiracy. the more complex, durable and water proof a phone is, the harder its going to be to repair or replace a component or battery. the nice thing is that now that the technology is mature and basically good enough to do anything fairly well, people won't need to upgrade for tech or feature reasons anymore. Now it will just be a trade-off between durability and water/dirt resistance, and repairability.
Also, people have no clue how to care for batteries. phones get left in hot cars at 100% charge, left in the sun at the beach at 100%. There is no BMS or hardware battery protection mechanism that can protect against that. Those batteries are fucked and will need to be replaced. And replacement means breaking the water seal around the phone, so it's annoying and expensive. it's just the way it is. you are responsible for your battery, and the better you treat it, the longer it will last.