It is not necessary to have a grammatical future tense to talk or think about the future. In fact, English does not have a future tense in the technical grammatical sense of 'tense'.
More generally, there's no evidence for the existence of human languages with the sort of lack of expressive power that you're talking about. All languages appear to be more-or-less equivalent in their expressive power, although of course that does not imply that exact translation is possible in all instances.
I was thinking the other day about that language that has no relative left/right and instead everything is based on (effectively) compass direction. The speakers reportedly have excellent direction sense compared to the average non-speaker. Their language is much more efficient at certain tasks we struggle with (English has crutches like "stage left", "starboard", and "your left" to compensate, but unless expected and practiced those are always effort/error prone. I myself fail at simple right/left way too often.)
Obviously this is a linguistic (and arguably cultural) trait with some value, without denying the value of also having relative kedtýright.
This language is unique (? or at least very rare), which tells me it failed to spread. Logical, as it would be hard for non-native speakers to pick up.
But that means "losing the evolutionary race" has no particular relation to the VALUE to us.
Would be OK to forget how to make stone tools because we don't need them for now?
Traits are useful in some circumstances and not some useful when circumstances change, who say you would not miss them in the future?
Knowledge is knowledge, it adds to our always imperfect understanding of the world.