mIRC gave people years of support with both UTF8 and code pages. During that time, anyone who wanted to could have made the switch easily. There was plenty of time. Khaled has decided that mIRC is going to move toward the future now instead of providing support to outdated methods of communication (code pages) even if there are people and servers who have not made the switch. Anyone who absolutely cannot or refuses to switch can continue using mIRC 6.35 without a problem.
Khaled has stated that he's not bring back code page support and has given explanations multiple times. Bringing it up again is not likely to change his mind.
IRCDs *can* support UTF8 nicks and channels. Many do. It's true that for those that do not yet support that, it may take a lot of work and time to update the software to support it. They have had many years since Unicode became widespread to do so. Just because some have chosen to ignore where everyone else is headed doesn't mean that everyone else has to waste time and effort propping them up on their outdated software.
Also, most clients have supported Unicode for a long time just like mIRC has. Those that do not support it yet are again outdated. Outdated software isn't worth using, imo. There are plenty of choices that support Unicode if someone doesn't want to use mIRC and they can easily switch. Holding mIRC back because some clients don't support Unicode is not a good reason by any means.
no one can force the whole world to use mIRC
By that same token, no one is forcing anyone to use mIRC. If someone wants code page support, they are free to use other clients or even older versions of mIRC. They aren't required to use the newer versions of mIRC.
