Sometimes things just don’t work out. Twitter certainly can’t be blamed for trying all kinds of different ideas, either by putting their own resources to work on them, or just acquiring other companies (Vine, Periscope, and many more - see list here:
https://en.wikipedia.org/wiki/List_of_mergers_and_acquisitio... ).
They have a product that is very valuable to many people, but those people are not enough, and the things Twitter tried just didn’t improve the situation.
They could expand and try to compete with Facebook, but that’s not going to work and will alienate their current core users, they could reconsider the 140characters limit (ditto), they could just stick to offering the same service in perpetuity with minor changes here and there, and hope for the best, and that’s what they are doing. They need to expand their users base and by extension increase their profits (more users, more ads served, and there is this whole network effect to consider).
The fact is, potential buyers are aware of that implicit users-base wall Twitter has hit a long time ago, and are probably not interested that much in contributing their own ideas in order to succeed where Twitter’s many leaders in the past failed to do. They should know that significant changes to the product will morph Twitter into something else, it will no longer be Twitter, and like I suggested earlier, Twitter doesn’t stand a real chance as a competitor to Facebook and other emerging/established networks.
I love Twitter, I use it every day and it provides me with a lot of value. I suppose it’d be best for me and others like me if they stay the course, so that we can all use it like we do today, and hope one of their future ideas will work out, all the while they are losing market share, and then eventually, inevitably, agree to a sale. The alternative would be someone else buys it now and Twitter will soon become something, and that will undo the company.