Table tennis has 4 problems:
1) If you do not start playing seriously from a young age, reaching a decent (2600) playing level is impossible. Even at 2600 a serious professional will make you look like an idiot when you play them.
2) The sport is too expensive. $25/hr for table time. $100/hr for coaching. $150/per month for rubber (if you are serious you will change rubber every 4 days which means $1050/month). I know a family who budgets $200k a year just for their table tennis activities..
3) Unless the players are very closely matched, practicing/playing is somewhat pointless and not a lot of fun. The better you get, the harder it is to find people to train with.
4) Even if you have an unlimited budget to help you achieve a decent playing level, unless you are a star from a very few select countries, you will not be able to survive on playing alone and you will end up coaching to make a living.
There is a saying "Checkers sells more than Chess" and that is why pickleball will probably do better than table tennis. The general population wants something fun to do. When an adult shows up at a club and plays Smitty Harimoto who screams every point and beats them 11-0, 11-0 and 11-0, they probably will find something else to do with their leisure time. Some people really love the challenge of table tennis and that is probably why most of the people here play. That is part of the appeal. However, the general public wants something easier and more fun to do when they have free time.
1. This may be a personal problem that is personally frustrating, but this is not unique to TT compared to other highly developed sports, and it is not something that I think affects the popularity of TT.
2. Maybe in some places this is an issue (like the new fangled PingPod in NYC), but in Dallas for example there are clubs you can play for $5-15 one day or $50-100 per month. Coaching is expensive in any sport.
You don't need to spend $150 per month on rubber. Option one is to get a durable rubber like G-1 or C-1 which will last months. Or buy chinese, which is $5-$20 per rubber. Once you get to 2500 level, you can get sponsored and start getting free equipment (potentially, depends on other factors).
3. True with many other sports too, and the solution is to be creative. First, teach them to feed you multiball. When they get to intermediate level teach them to block for you. That opens a huge array of drills. In exchange you can teach them. If they are serious and you are a good teacher they can hopefully increase there level close enough to eventually at least do warm up and drill practice with you. The problem with less players at high level is very true in pickleball too.
4. Yes, and true for most other sports too.
5. Not quite, in my experience table tennis is wildly popular in a casual setting. Also, if this was true then hardbat TT would be much more popular and developed in the US. Pickleball is mostly popular for other reasons (social aspect, tennis derivative, unique gameplay, etc.), not just because it is easy to pickup or play.