Big breweries holding publicans to ransom mostly ended in the late 80s/early 90s when the monopolies and mergers decided to limit the number of pubs brewers could own.
Some would say that the culprits these days are the big tenanted pub companies with 1000s of pubs each: punch, enterprise, etc. The counter argument is that if they charged less for the beer they'd charge more rent to maintain margins (and stay in business. which is touch and go at times in the current climate) so they would argue that they're sharing the risk with the tenant.
There are still the old family/regional brewers who both brew and have a few hundred pubs (Fullers, Robinsons, Brains, St Austell, etc) but they are tiny compared to the big pub companies and are relatively fair to their tenants in my opinion, although the ones whose businesses fail probably disagree!
Of course, they are all utterly dwarfed by the big brewers, of which there are probably about 6 globally, but they don't own pubs. Heineken are probably the biggest in the UK since they bought Scottish and Newcastle a few years ago. When you start to read up on who owns which brands it's incredible how many well known ones (especially lagers but also the likes of doombar) are owned by so few companies.
The opposite end if the scale is the microbrewers, who thanks to a significant tax break can undercut all the others so can compete with the big brands to some extent without having to spend on marketing, as long as they don't get too big. This is a really good thing in my opinion and some of them do make some really nice beer
Oh and yes, wetherspoons are the crc/tesco of the pub world. Massive buying power, drive down prices, more people buy from them so their buying power increases.Vicious circle.
Fundamentally though the problem for pubs is that I and so many like me are sitting at home watching tv/on the Internet with a supermarket bottle of wine whereas in the 80s i'd probably have been stopping at the pub for early doors each night. I love a good evening in a nice real ale pub but tbh I don't do it often. That said, the pubs that struggle most are the carling/fosters type drinking pubs. A well-run ale house or quality food-led pub can do extremely well at the moment, subject to location.
Hmm, long post. TL;DR: it's complicated and always changing, but there's still room for good pubs and good beer. Oh. And I probably won't invest in that pub, personally, but good luck to anyone that does.