It is becoming very expensive and difficult as the moats these companies have been able to build are enormous.

One upside I see is that phone hardware slowed in innovation and most changes are now software. This allows a new comer to build a phone over 2 years and have specs that are still good enough. This was a huge issue back a few years ago when a "kickstarter" was created and two years later the phone was unusable because of the poor hardware specs.