It is seen that EGT are of the order of 600°C (What is a normal EGT range of a jet engine?) for aviation turbines and nearly the same for stationary turbines. Why can't high temperature exhaust gases are further harnessed like adding another stage in turbine section that extracts more energy?
In aviation turbines can't we just add another turbine stage like another low-pressure turbine mounted on another spool? For land-based gas turbines we can somewhat utilize these high temperature exhaust gases in Combined cycle but what about aviation engines?