It might be difficult to measure evolutionary progress, but that is no excuse for ditching the whole concept:

Evolution is an optimisation process - similar to a genetic algorithm. We even know what the fitness function is - and so can see what is being optimised. Optimisation processes are - by their very nature - powerfully directional processes.

There is a way in which such a process could fail to be directional - if it had too large a mutation rate. That might happen if our planet was extremely radioactive, or if it was frequently bombed by large meteorite strikes. However, in practice, neither of these things applies.

- http://alife.co.uk/essays/technology_explosion/

A brief examination of the history of life shows that it is characterised by an accumulation of "survival technology" - i.e. either adaptations or technology.

In particular, the biosphere is accumulating "natural technology" that helps it more rapidly identify sources of potential energy - and degrade them in the process of constructing offspring.

The accumulation is progressive, cumulative - and inexorable in character - and the resulting ratchet mechanism provides evolution with a powerful progressive, directional character.

- http://originoflife.net/direction/