The site is not dying considering the Tennis Elbow tour keeps growing with regular new members coming in, and above all, always full tournaments.
The level is actually really huge, and there is a real dynamic hierarchy with a regular high level top20 and a few guys still playing after 2 years of competition.
I really advice you to try this game which is the best ever made for Tennis. Watch also the history of the competitions played. There are great champions on this tour and the results are regularly different as the form of the day has a big impact in matches.
Ex : The winner of Wimbledon was close to loose in early rounds of US Open against a non-seeded player, because of a lack of form.
As the match are demanding mentally, you even have to carefully manage your tournament schedule if you want to stay at a high level longer : if you play too much, you will have a burnout and will loose your level

I played the Top Spin 4 tour for 2 years I think, was a regular top 10, and I can tell you the Tennis Elbow is far more interesting. With the Chat, every players talk, organize practices etc. We know each other very well so it's great

Personally, I actually think the key issue is the website which is completely out of date. But there are apparently no developers in the community that would be willing to help the staff to build another one, so I don't know.