I completely agree that you do need a unique selling point as what most people seem to forget in desperate times is that this is a business. In any business, you need to grow, adapt and you need to find what makes you stand out from the rest and gets you noticed. For actors, that means having a high level of castability for either television, theatre, certain things that make you a clear choice for certain characters whether thats your physical appearance, voice or whatever. Now this is different for everyone and how you go about promoting this is your own (or agents) choice.
Of course, Talent is a must but it is naive to believe that this alone will get you to the top (where ever that may be). In an ideal world, yes, this would happen but unfortunately, like every business, people are in it to here to make money (maybe not the actors...). You can be a phenomenally good actor but as Emily has stated, she in a horrible casting bracket amongst millions of other girls trying to do exactly the same thing and the need to have something that sells you as well as your acting talent is essential.
I'm not saying you do a Tesco and believe that you can do and play everything but I agree that you need to have little things that can set you apart from the crowd. Some people might not even realise that they have one (or many). It could be something that you learn or acquire or maybe something that you're born with. This could be height, weight, dancing, amazing personality, instant likeability, musical ability, magnificent stage presence and so on. It can even be a subtle as someone having the most amazing eyes. Step forward Daniel Craig.
It is extremely hard to break though and so many factors go with it. Talent, hard work, luck, right look, right person, right place, the right mood, the right circumstances, saying the right thing (you get the idea). Having all this combined and more is ultimately rare and that's often the case with actors not ever reaching the career highs they crave and in some cases, deserve.
So I agree that you need something unique about yourself that makes you more attractive to agents and casting directors. It's not easy by any means, in fact, it's bloody difficult.
I also understand the counter argument of people who some deem some actors to be maybe not up to standard and still getting plenty of work, getting an amazing agent, getting high profile jobs, getting their break because of this and that but unfortunately, that is the business. That is life. It's not fair and you just have to get used to it and accept it. It just might be that their unique selling point got them there so you just have to believe that it could happen to you.
Finally, in regards to your looks there Emily, I think you're really pretty. Pretty in a gritty way. But still Pretty. Pretty.