Why would anyone want a newer scripting language? That is like wanting to build a house from new bricks. If you know the old language, you can use it. If you don't, then perhaps you should not be messing with the system initialisation?
Its not like normal admins have to write these scripts - the people who manage ports supply them for you, and have a tool that puts them in the right place.Most people run OBSD because they want to have a system that runs their apps, not so they can experiment with the boot process. OBSD boots really fast. (Unless you screw up your fstab - like I did last week - In which case it might not boot at all).
Do you also complain about the type of pipe clip your car manufacturer uses on the under-bonnet pipes?
If you want to use Java to write a systemd replacement, then go ahead - I wont stop you. Do like Linus, and write your own damned OS.