Miyajima is more of a chill out place - it's a small island. If you like walking, the outdoors & nature then you can follow long hiking trails & see other parts of the island & the beaches too! If you are prepared to entertain yourself it's a great place. It has a village, temples, a mountain and lots of animals esp. at night in the forest ( I went on great camping trip there once & returned on other trips to stay in very swish ryokan - which were fine too but I'll never forget the nights outdoors in the forest - magical.)
So if you would like 2 days of quiet, healthy living then it's for you. Get a hiking map or just wander www.miyajima.or.jp/english/course/course.html
Momijiso looks quite simple, ie. basic level not a luxury ryokan. Make sure you read the reviews - there's a very funny one on TA someone complaining that the staff couldn't speak English! The room was spartan!! haha The place was locked at 9. Plus there were no foreign channels on tv!!! hahaha ... they did know they were in Japan, right? Beats me why some people travel at all.
I laughed so hard it had to have been posted as a joke.
Many ryokan lock the doors relatively early (but of course will let you in & out if you are going somewhere in the evening) but what were they expecting to do on Miyajima? Tanuki spotting maybe, it's not like you can go clubbing...
And note a reviewer says they only take cash - not uncommon in Japan (as we all keep telling people on T/A) Hey everyone, take cash with you!!! and keep a reserve at all times, you aint going to get mugged in Japan & ryokans &hotels have safes if you need them.
You might see some other options here:
Hiroshima is a city with the usual city stuff, it just depends on what you are looking for as part of your trip.