A 1998 astrological survey indicated that the universe was expanding at an accelerating rate. The idea of dark energy arose to explain it. In 2016, additional data on stellar luminosity discredited dark energy as causing accelerating expansion. Dark energy was simply a case of insufficient data viewed through the wrong lens.
The apparent manifestation of dark energy is a consequence of analyzing the data in an oversimplified theoretical model – one that was in fact constructed in the 1930s, long before there was any real data. A more sophisticated theoretical framework, accounting for the observation that the universe is not exactly homogeneous and that its matter content may not behave as an ideal gas – two key assumptions of standard cosmology – may well be able to account for all observations without requiring dark energy. Indeed, vacuum energy is something of which we have absolutely no understanding in fundamental theory. ~ Indian theoretical physicist Subir Sarkar
The Milky Way has far fewer neighbors than theory suggests that it should. The galaxy is in an abyss about 2 billion light-years wide.
With the Milky Way in a void, the apparent rate at which the universe is expanding depends upon how it is measured. Measurements based upon the cosmic microwave background (CMB) radiation suggest a slower expansion rate than measurements of nearby supernovas. The actual expansion rate is probably even slower than the CMB rate.
If you don’t account for the void effects, you could mistake this relationship to indicate there is too much expansion. ~ American astrophysicist Benjamin Hoscheit
Dark energy can also be discounted by facile assumptions about the structure of the universe which conjure it.
Einstein’s equations of general relativity that describe the expansion of the universe are so complex mathematically that, for a hundred years, no solutions accounting for the effect of cosmic structures have been found. Coarse approximations to Einstein’s equations may introduce serious side-effects, such as the need for dark energy in models designed to fit observational data. ~ Hungarian astrophysicist László Dobos in 2017