how does one find out what the level of participation is?
Guild Description is usually the best indicator of what is expected of members.
Why would someone join a guild and not expect to take part in the activities as a trade-off for the benefits of being a member?
Finding a perfect fit for the level of support you provide/expect is rare. So usually someone will try to find a guild that meets their minimum expectations. Things they don't really want to do they'll either do anyways because they value the guild or hope for some tolerance if their contribution in other areas is valued.
Some things that you might wish were required wind up often not being so because it's painful for the leadership to enforce it. Things like trade etiquette, aid requirements, etc are a major headache if you want to enforce rules. Most guilds therefore just don't have such rules. Others have them but don't really enforce them.
And any number of issues arising from same, about which people may have ideas. I have personally become a guild of one for the time being, is this a viable position to play from, does the game support small guilds? I will probably join another guild in time but the whole thing was a bit too close to the politics of real life for relaxation time and don't really need that in-game...
A 1 person guild is viable for many things but is far from a perfect solution.
There are no activities that are outright blocked from you.
You can't get the boost of a championship win from GE unless you have at least 3 people, but you can still do GE (and unlock it easier than an inactive larger guild).
You will find GBG to be more challenging without people to share the burden- but that's not entirely a bad thing as you will be naturally insulated from the lack of parity at the top of the standings - it might even feel like a good system to you if you never find your way to diamond.
Guilds are often the best option to get support for levelling your great buildings (usually by 1.9 these days). You can find global threads instead often - but it's more work to do so.