Wouldn't say the airline is run-down. Average age of their 777's is around 5 years, but of course are a bit older than their 787/A350 long-haul planes. Any complaints about something being run-down related to ET tend to be more directed to their ADD hub or regional fleet - but they are working on it.
Business class (Cloud Nine) on ET 777 is a lie flat seat with plenty of leg room, though in a bit of an odd 2-3-2 configuration as discussed here:
Ethiopian Best Business Class Seats?
They've been known to sub in 787 on short notice, but that route has been fairly solidly flown by their 777 fleet recently.
I've found service in cloud nine has always been top notch - friendly and attentive.