There's some confusion here. Thermodynamics involves changes in going from an initial state to a final state. The path taken between those two states can be either reversible or irreversible.
The process that moves the system along the path between the two states is reversible if and only if two conditions are fulfilled: (1) that a microscopic change in the external conditions would cause the direction of the process to reverse. The other, (2) is that the system always be in a state of total equilibrium. Point (2) implies that an equilibrium process be infinitely slow. (There are a few exceptions to this but we won't go there now.) All other processes are irreversible.
Thus it is clear that essentially all real processes are irreversible.
Nevertheless, most all thermodynamic variables are independent of path. That's a consequence of the first law. So it is always possible to envision a reversible path and to calculate thermodynamic properties for that change. The same thermodynamics properties apply to the real process.
So changes thought to be irreversible 100 years ago are still irreversible. But it is possible that we have found new reversible paths between states. That may make calculations easier, but it won't change the numerical answers.