Accelerated? Increased? Sped up?
Yes, I guess all are descriptive of a group becoming faster so I'm at a bit of a loss as to why you would pick out my use of "improved" as your choices pretty much describe the same thing.
But it is not necessarily an improvement in the ride. Indeed, it may make it inaccessible to some.
I said the riders had improved I did not say the ride had improved. Does it mean the ride has improved? It depends on the measure I suppose. Increased speed and stamina opens up new possibilities leading to quieter, more scenic routes, better views, alternative cafes for example. I know for this particular ride people who had stopped using it have returned so possibly it is seen as an overall improvement by those individuals.
Inaccessible to some? Yes but no one has stopped using the ride, others have returned but it is harder for riders in the group which rides at 12/13 to make the jump. The solution? Perhaps accept one needs to put a little extra effort in for a few weeks. Create a new ride, step forward and offer to put on a group which is going to ride at 14/15. It's not a difficult task and people should not expect to have everything handed to them on a plate.
I assume better means faster to you, but it could mean more efficient, less straining, able to ride steeper max gradients, or other things.
But this may be ableism more than sexism so I guess we are straying offtopic.
Better does not mean faster to me because I recognise all cyclists are good cyclists, no one is better than another. Through natural ability, training, experience and host of other factors some riders are able to ride further, faster, climb harder etc. than others. It doesn't make them better simply faster. As for my own improvement as a climber, yes I measure it in terms of speed on climbs I know well but also by successfully tackling climbs which would previously have been a significant challenge. I know this increase in speed and ability to tackle harder climbs is because I have improved and am better than I used. It comes through better technique resulting in greater efficiency, less straining, greater endurance and so on. Better is in relation to myself, I am not better than anyone else.