I was given membership of the Wine Society as a leaving gift from a job I left more than 20 years ago. So I didn't pay the one-off membership fee - they call it a lifetime share, and it's organised as a cooperative - which I see is now £40.
You can buy good value, reliable wine from many more places these days than you could 20 years ago, and without paying a membership fee. That said, I've continued to buy from the WS among others. I find their wines pretty good, and their own-label ones particularly good value; the website and delivery arrangements are good; and I like the cooperative structure, owned by the members. They have a good range, including more out-of-the ordinary things like buying en primeur and storing wine for members until you need it, and they're good for gifts at Xmas and other times of the year. They also run tastings, which are a good way of trying before you buy (and trying things you wouldn't buy).
The other online outfit I've regularly bought from is Laithwaites, which used to be Bordeaux Direct and I think is the same people as the Sunday Times Wine Club. Also good value, with a different style: a little more ebullient, where the WS comes across as steady and reliable (this is starting to sound like a tasting note!).
You pays your money, and you takes your choice. The question is whether £40 up front is worth it for you. It has been for me but, as explained, I didn't pay it in the first place!