Ali is a conundrum - he isn't the best spinner in the country by a long chalk but...all the ones that are better are either in their late 30s (Batty), horribly one dimensional misfits(Panesar, Kerrigan), or leg spinners. Yes, Rashid is a better bowler in second innings conditions but England have made it clear that they are not prepared to use their pace attack the way Yorkshire do to protect him early doors and see him as the second spinner so...
What would you do? Ali is a decent counterattacking number 6-8 in international cricket (okay, if I were being pedantic I'd say so will Rashid be in time), doesn't let anyone down in the field and has improved markedly as a bowler. For the time being, especially in English conditions where seam is more prevalent, he does a job and does it reasonably well. Whether he should be in the team in Australia next time round (no - he'd get murdered) or even in South Africa (no - four seamers plus Rashid is plenty) is a different matter. Mid term, I suspect the hope is that Ansari lives up to early promise and gives them the option of a more solid version of this six man attack, taking Ali's spot.
Bigger problem here is that England are about to extend the Jonny Bairstow problem. Whats the betting poor Jonny gets shunted down to seven despite doing well at five just because that's where the keeper bats, goddamn it. Since coming back into the team he's done well (better than anyone outside Cook and Root, that is to say) but this move will result in us still not knowing what his role should be or if he is quite good enough.