The answer IMO has been touched upon by others on this thread but not openly.
The simple answer is that we are waking up to the fact that tennis, football, rugby, cycling, athletics etc etc are no longer sports at the top level but an industry - and unless they are approached in that way you can't have success.
The skill levels at the top of all those events are undoubtedly higher than they were just twenty years ago - I'm not convinced though that this makes them more enjoyable or exciting to watch.
There's no reason to think that because money has been put into improving performance that something is no longer a sport. Much of the money is spent on coaching rather than spent on wages for players, which helps improve the grass-roots and brings more people into the sport. From this larger pool of athletes there is a higher level of competition and a higher number of better elites emerges.
Enjoyable and exciting sport comes from close races or games, which still occur. Whether that's racing at 40kph or 30kph doesn't really matter - it's the competition, not speed that makes it exciting.