You are correct when you say that not every woman can orgasm from penetration, but the figures are roughly 70% of women who can't, which actually puts your partner in the largest group, the most common, the one that is often the usual, so my advice about this aspect would be as follows...by all means experiment with different positions to make her orgasm from penetration, but don't make this your mission, your one big goal, because she will pick up the fact that you are constantly trying to do something to her that doesn't work and THAT could put her off sex.
Instead I recommend focusing on what she CAN do and making that more interesting. For example, I cannot orgasm from penetration alone and trust me, i've been having this sex business for over ten years and I am very comfortable and confident but the problem is, most women cum from clitoral stimulation and this is not touched much, if at all during sex. Imagine your missus making it her goal and ultimate mission to make you orgasm from say....touching your thighs or balls and nothing else? Anyway, back to the point, I cannot orgasm from penetration alone, but....I can reach orgasm if my clitoris is being stimulated while he penetrates me. I can use all different types of vibrators, or mine or his fingers.
My womanly advice? Treat foreplay as sex...because whether you guys like it or not, I'm afraid that for the vast majority of us women, orgasm doesnt happen through penetration. Treat penetration as another part of foreplay and don't build up the actual penetration part as the end goal, the thing that must be done, or the most important part. Instead treat oral sex, fingering, massages, dirty talking, role playing, kissing, nipple and breast play and all the rest...as the main events. Of course, you can still have penetration as often as you wish, but don't treat foreplay as something to get her worked up and wet ready for sex. Instead treat the foreplay as an extended session of tactile stimulation with your fingers tongues and sex toys and more...until she orgasms from that without even needing penetration. Alternatively, go even further with the foreplay that usual, before the penetration, until she is close to orgasm and then during the penetration, continue to stimulate her clitoris.
Not being able to orgasm from penetration is unlikely to be the reason she is not keen on having sex, UNLESS you are making the penetration the main event and skipping all the bits that really titilate her hot spots.
My biggest tip is to remember men are more visual and women are more "mental" This gets overlooked by men easily because, well put it this way....men want to blow our minds and give us intense pleasure, so they do what we all do....we imagine what would please OURSELVES, what would blow our own minds and then try to replicate a similar experience for our partners. Men like to be very physical (Lots of touching parts of the body) and very visual (Different positions, lights on, cum on her face etc etc on and on) Which is all good of course, but women have a different brain process than men....we are slow burners, we like to fantasise and we cannot flick a switch (Not often anyway) and "be horny now" Women tend to get more turned on with a slow burn, putting ideas into her mind, teasing, talking to her to put fantasies and memories into her mind and we also love to know we are really desired.
So my biggest tip for this one if you want to get your lady in the mood more often, is this: Try to initiate sex hours, all day, or days before you want to get jiggy and when you do initiate it...try not to initiate it with a physical gesture (So no grabbing and honking her boobs or ass) or a visual gesture (No whipping out your body parts to tantalise her) ....Of course, you can use these methods too, but at first, try not to use them because it will help you learn to use HER sexual imagination. It will help you to stimulate her mind with words. Just one sentance, if spoken correctly and appeals to her fantasy, can have a woman turn from stone cold to a jibbering horny mess. Use her fantasies and imaginings to make her swoon...with words, promises, hints, teases and of course...comments on how sexy she is (but not just her physical features. I also recommend complimenting her on something she did once during sex, tell her why it blew your mind and much more, to get her feeling desired and sexy...way before bed time.
As for sex toys, ask her. Some women love them, some thought they would hate them and then became huge fans and others just love em outright, but surprising a woman who has little interest in sex, with sex toys and lingerie, has the potential to make her feel like you are pushing for more, or it could make her feel a bit "forced" into putting on a show, or having sexual activity that she has little interest in.
Please also bear in mind that women especially can go right off sex if something isnt right...we really are more "mental" and because our minds are our largest sex organ, the one we use most to feel sexy, get in the mood and even orgasm, can you imagine how it stops working when we are busy/stressed/tired/pissed off etc and unfortunately there is so much in life to add these stresses or busy schedules that leave us drained and there is not much I can suggest other than help her more (to let her recuperate some energy or remove some stress) and never ever stop making her feel like the sexy desireable women you love. When life gets in the way, we stop doing all those things we did at the start, to impress our partners. Bring some of that back and you may notice a change.
Most complaints I hear from female friends are that she feels she is taking on the lions share of the general burdens of life and he is only paying her that sweet attention when he wants an orgasm (sex) this is the most common complaint. Not that guys are doing anything wrong, but we all think and work differently. Maybe you appreciate being left alone to get a task done, as you can do it without distraction, this then makes you think that she would feel the same, but she might be wishing you'd help. That is just one of millions of examples on how we miscommunicate as couples and end up feeling meh at times. We all do it! lol
Wow, sorry, I hope this helped somehow, I rambled again xx