That is not the labor theory of value. The whole point of LTV, at least in Marxian economics, is that workers can't be payed according to their socially necessary labor, because a surplus labor is extracted.
Besides, LTV as a theory is meant to be a description of the world as Smith, Marx, etc. see it, not a prescription for how things should be done.
You're right that it is descriptive and not normative.
But the underlying belief of paying someone according to their effort, is very much based on the same premise.
What I'm saying is that nobody is _really_ paid according to their effort, experience etc. because those things cannot be reasonably measured.
The typical process of determining compensation is based on negotiation and power. In some places the process is more democratized and rules based. Both of these are only to some degree related to actual effort, experience and so on. This discrepancy becomes larger the more people are involved as well.
Besides, LTV as a theory is meant to be a description of the world as Smith, Marx, etc. see it, not a prescription for how things should be done.