General Relativity is quite exotic from the perspective of everyday life, and the theory and math behind it is quite complicated. Yet, it works. We can observe and measure its effects with extreme accuracy, and we have without exaggeration millions of actual tangible empirical corroborations that it is indeed a real thing, and actually describes how the universe works with an amazing amount of detail.
It also has practical applications. Or, perhaps more precisely, many practical applications need to take General Relativity into account for them to work properly. GPS might be the most often cited example: If relativistic time dilation effects were not taken into account (because satellites are much higher up in Earth's gravity well than the surface), results would drift very considerably quite quickly. Also things like atomic clocks actually need to take into account their distance from Earth's center of mass and adjust their results accordingly, and fully in line with the General Relativity equations. And those are just a couple of examples.
Needless to say, the accuracy of General Relativity has been measured and tested to death, and it just works.
Quantum Mechanics is every more esoteric than General Relativity. Yet, in many ways it's even more supported by actual observations, measurements and testing, and has even more practical applications that can actually be used in real life. Not only are there many applications where quantum effects need to be taken into account (similar to how relativistic effects have to) and can be directly observed, but there are many, many situations where the quantum effects themselves have practical applications.
Particle physics is closely tied to Quantum Mechanics, but it is, perhaps slightly adjacent to it, and often slightly less esoteric, but still quite wild at times. And we have an absolutely enormous amounts of practical applications for it. Heck, the very computer you are using right now to read this would not exist without the results and practical applications of particle physics.
Now consider String Theory.
It has been around for over 50 years now. How many observations, measurements and tests do we have that corroborate its results?
None.
How many practical applications do we have where the effects of String Theory need to be taken into account, else results would be incorrect or drift, or the application would just outright not work?
None.
How many practical applications do we have that use the effects described by String Theory to their advantage? In other words, how many practical applications has String Theory produced?
None.
By this point it should have been discarded as just one of the myriads and myriads of other hypotheses that were seriously presented but then discarded due to lack of evidence.
Yet, for some unfathomable reason, many scientists are still taking it seriously and studying it, even though to this day they have zero evidence for it. It can't be measured, it can't be observed, it can't be tested, it has no predictive power, it has no practical applications. Nothing. Yet, it's still being taken seriously.
It's astonishing.
