The common components are irrelevant. Even Apple still has components manufactured by Foxconn, buys RAM and flash from the same vendors as anyone else, uses ARM's ISA, etc. The phones made by Xiaomi et al are perfectly capable of running the same apps as Apple's from a hardware perspective.

The difference is that now if someone wants to make a competing store for iOS apps, or a competing client app for Reddit or Twitter, the incumbents use the DMCA and remote attestation and similar anti-competitive levers to lock those competitors out of the market and governments have been letting them get away with it.