The only time I've gone with a group riding holiday I had a great time in basic accommodation but the key things were:
1. Turnout for the ponies close by for checking - optional indoor shelter of some kind but we needed to be out making sure they were getting on the first night and the other nights we were out all day and wanted no unnecessary hikes in the dark to check ponies once we'd got home aching and ready for a rest!
2. Hot showers, drying area for wet clothes (and tack!), basic cooker and heating of some kind. We didn't have a log fire but tbh after a day hacking I doubt we'd have wanted to be carting logs in.
3. Superb off road hacking for miles without access issues, grumpy neighbours/farmers, or a trek along a road to get there. This is why we chose the place, the riding, so put info of any decent options, the more the better and if you can give out printed maps, laminated ideally, most folk will leave them behind but all will appreciate not arriving at a bog or an unpassable barb wire fence where the OS says it's clear. Local knowledge and contacts you have, perfect.
4. Access and parking for lorries and trailers - as we had 8 riders and several vehicles, think of the space and turning for them all and most groups will pack in as many as possible to reduce costs.
If I were going alone rather than riding, it changes a bit:
1. Basics as 2 above but probably the log burner and a view or a snug and SkyTV. I could be flexible over wet weather choices but not a bland beige and tatty board games for a single middle aged woman who wants to walk, see views, maybe visit a couple places of interest, and needs info on a decent cafe and veggie friendly eating..
2. If I'm paying for somewhere myself then I don't want damp doggy smells - even if I had a dog and wanted to take it I'd want dog friendly space that didn't impact on carpets/furniture as I'd be worrying the owner would charge me for mess and if the dog was wet and couldn't be kept anywhere with a hard floor and a supply of old towels or something, and a mop.. then I'd feel frustrated.
3. Key on this one would be clarity of information - whether areas were off limits, had rules (indoor and out), local facilities, hiking routes, places to see, eat, get that email/phone signal during daylight hours at least daily to check home.
4. The host attitude - I stayed on a B&B on Mull years ago and the family attitude stank, they put us in a huge bland living room and pointedly walked out to sit in the kitchen, possibly they thought it was polite but the way they did it looked as if we were not worth talking to and they couldn't be bothered doing more than bare minimum to get money off us. OTOH a lady on Islay all but adopted us, took us round her pottery, invited us for tea, gave us all the places to go including a few non-touristy ones, arranged for me to go hacking at a local trekking yard even tho it was closed as her daughter knew the daughter of the family and said she'd have to exercise her own pony anyway so was happy to take me with her, just little things, getting from money making to giving a great time. Seeing each booking as an individual not part of an annoying necessity but potentially someone that might like to be alone but might want an opportunity to do something entirely different.