It's hard to be great at something. Often it's said it takes about 10,000 hours to become truly great at something - and that's not just putting in the hours, that's working hard. (The "10,000 hour rule" is mentioned repeatedly in some books and article, such as "Outliers." It's not a strict rule, just a rough guideline) While we can debate on just how long it really takes to be truly great, and find all sorts of exceptions in both directions, it is a good approximation of what it takes, whether it's in sports, arts, academics, or most other fields.
The problem is that 10,000 hours takes 10,000 hours. Most people have jobs or school, and other obligations such as family, etc., and can't devote their lives to this. Suppose you do three times a week for two hours. Then it's going to take 33 years to get to 10,000 hours! The problem in table tennis is by that time you'll probably be past your physical peak. More importantly, if you take 33 years to get to those 10,000 hours, most of those 10,000 hours are wasted as you forget much of the early training, i.e. 10,000 hours over 33 years isn't the same as 10,000 hours in ten years (i.e. about 20 hours/week). It needs to be a bit more condensed.
What does this mean for you, the average player who can't put in 20 hours a week for a decade? It means you probably aren't going to be world champion, or even seriously challenge the players who compete to be world champion. It's a bitter pill to swallow, but someone has to tell you the truth.
But guess what? Anyone can become very good at something, and it doesn't take anywhere close to 10,000 hours in ten years. Pick out the aspects of table tennis where you can be good, and develop your game around that. It may take 10,000 hours to develop a truly world-class game, but it doesn't take that long to develop a very good serve, or a very good loop against backspin, a very good block, or any other specific aspect of your game. They key is to develop it properly, watching how the top players do it, perhaps working with a coach, and focus on developing it until it is very good. You can probably do that in 100 hours. (My serves are considered very good by most standards. I developed them mostly be practicing them 20 minutes a day, five days a week, for about a year. That's a little over 80 hours total.)
Here's the double pay-off. If you develop one aspect of your game, other parts will follow. If you develop a very good serve, then you get lots of follow-up shots, and so you develop a very good attack. If you develop a very good loop against backspin, you'll get a lot of blocked returns, and you'll develop a very good follow-up to your opening loop. If you develop a very good block, you'll develop ways to win points that way, either with put-away shots after you've blocked your opponent out of position and forced a weak shot, or numerous other ways - more aggressive blocks, change-of pace blocks, pure steadiness, etc. And so on. (The three examples I give here are ones I myself went through.)
And here's the triple pay-off. When parts of your game become very good, your overall level will tend to go up, and you'll end up playing better players - and they'll force you to raise your level to an even higher standard. So becoming very good at one shot often improves other aspects of your game, and brings up your whole level. One key here is to understand the whole process. Developing one shot doesn't mean it ends with just developing that shot - the end is to both developing that shot and the other techniques that go with that shot, i.e. setting it up and following it up.
So what are you waiting for? If a "pro" has to put in 10,000 hours, can you do 1% of that, and put in 100 hours to develop one aspect until it's very good, knowing the double and triple pay-offs that will follow? Go to it.