The problem with the Shotclock is that it is seen as a gimmick, which in truth is a fair comment, anything which dare it be said artificializes the true nature of the sport could be seen as a gimmick, namely having ball in hand, playing a frame with just six reds rather than fifteen, and other requirements made for an event such as needing one ball to hit a cushion
Obviously, those that I've just mentioned above all come in events which are indeed seen as gimicks, such as a time limit for a match, or requires a shot to be played within a short time frame.
However, there can be an argument that the game is artificialized in some of the rules the game uses to great effect, such as the disqualification of a player for three fouls and misses in certain scenarios in a frame of snooker, whereas other scenarios do not result in disqualification for three misses.
The opposing argument there is that these are covered by the rules and apply in "normal snooker"
The shotclock in eight ball pool works because it is arguably very generous. Considerably more so than a shotclock which is included in what is otherwise a "straight snooker format". A successful shotclock needs to be one where players aren't under consistent pressure but that players are aware of its presence. Of course in the shootout, where slow play tactics can play a considerable role in influencing the outcome such generoisity isn't an option.
I do think there's room for a timed format for snooker. Timed formats have been successful in billiards, where players may have 30 minutes total time to play at the table. It would be interesting to see how a billiards format, i.e. a match played over a set time, or players having a certain amount of time to play at the table would work.
However, like any gimmick, it should be an occasional rule format to aid variety, and not the rule which has a bearing on careers and rankings