some major technical challenges that Bitcoin developers face when implementing new upgrades includes the fact that they ensure compatibility with existing hardware and software. This whole process is tiresome as it involves extensive testing and collaboration among developers.
It is not as tiresome as you think it is. If you are a developer working with a team of developers who adopted certain standards of coding and making updates, you will understand that it is not difficult. The only thing that is needed is an agreement (consensus) and the implementation is done.
It will only involve testing and retesting for compatibility if you are deviating from the already established protocol (hard fork) and bitcoin does not such such situation often.
so my question here is without Bitcoin developers, can Bitcoin system still function well? if yes, I will be waiting for your replys and reasons. Thanks.
Yes, it will function very well. Infact, I have worked in such a situation that after making some updates in a e-commerce app, the majority of the users wanted the former version of the app. I and my team members had no choice than to reverse to the former.
Not all upgrades are necessary and for bitcoin it is just for the purpose of the security of the system and scalability of bitcoin that developers keep working on the bitcoin code.