The short answer: Depends how determined you are. The fitter you are, the less determination it’s going to take – and the more route options are available. I’ve had desperately unfit people enjoy hiking Table Mountain more than people of average fitness; the discerning factor is determination. A lot also depends on your expectations and interests. If you have a solid sense of adventure, then you would enjoy a scramble route, which takes the focus off fitness. Equally, if you expect it to be a walk in the park, then you need a good fitness level to carry you through the inevitable mental slump resulting from your false expectation.
Looked at from another angle, one could ask the question of how fit you must be in order to enjoy it. While some people have a masochistic approach to adventure and sport, most of us prefer to derive some enjoyment from it by not extending ourselves to the point of collapsing; so taking much strain on the hike (due to lack of fitness) tends to rob you of the enjoyment of the hike. Of course, persevering through the discomfort and perhaps also stepping outside your comfort zone adds a lot to the eventual sense of achievement when you reach the summit, but for some it’s not worth the price of labouring up a mountain in the blazing heat or cutting wind.
Yet another consideration is your love of nature. If you thrive in the great outdoors, then you are more prepared to get tired and face challenges on the ascent because of the distractions that the environment offer; a non-nature person only has eyes for the summit and has to endure the rigours of the ascent without the distraction that nature or the environment offer. What makes the question of fitness even harder to answer is that stamina also comes into play: you might get out of breath quickly, but a short rest and you’re good to crack on, and on and on… At a leisurely pace and on a long hike, a person with stamina and low fitness performs better than a person with average fitness and low stamina.
The bottom line: if you’re not fit, you need something else in order to sustain you in order to enjoy the hike, either determination or stamina, or a sense of adventure (combined with the right route choice), or a love for nature. Table Mountain hikes exist for every type of hiker, so it’s important to match the route with your fitness, preferences and expectations.