There already was thread (https://www.spigotmc.org/threads/bstats-instead-of-mcstats.246734/) about this year and a half ago, but nothing has changed since then.
The mcstats.org seems to be abandoned (last commit 2 years ago) and has big stability issues (the site seems to have been down for several months). So, maybe it's time to do something about it?

There are several options that I suggest to do:
1) Write own metrics service (as md_5 stated in thread)
2) Choose another metrics service and contact it's author about implementing (I suggest bStats)
3) Wait for mcstats to work again
4) Deprecate (and then remove) Metrics class if none of the above has happened

Also, if the metrics are to be changed, it would be good to get a new functionality. Like registering metrics directly from server implementation, without any additional classes.

Sorry for the mistakes (if any) I'm still learning English