I generally agree with you, but in this generic case, phones are actually truly packed to the max. Similarly to how you could easily fix your older car with just a few tools, modern engines are so complex that such home-twinkering is impossible. Phones go in the direction of having less and less separate parts, which is bad from a repairability pov, but the reason why these gigantic screen sizes are the new norm is also the side-effect of having to put n cameras, 5G, a huge battery, LiDAR and what not into a comparatively small body, while at the same time making it dust and water proof.