Hi, Bill. that is a very good question. The key to getting your wife to really see and treat you as her equal would fundamentally involve adjusting your communication strategies as a couple to ensure you both participate with each other as active listeners and contributors. Sometimes, communication patterns in relationships can be extremely damaged or broken so needs, hopes, fears and desires are not being actively communicated nor received. If she is highly critical and demeaning of you all the time, I can understand how you feel shut down and reluctant to engage her on most anything. For this to be relearned, it may be very helpful to consider couples counseling as a forum where the two of you are taught how to communicate effectively, with compassion and empathy for one another. These things can be trained and once the communication returns to effective and equal, the relationship can rebound.
Another factor would be to try to expand on your relationship so it encompasses new, interesting opportunities that the two of you can embark on together. Adding excitement and variation can enhance relationships and help them get out of ruts as you can grow roots in other directions as a couple rather than staying firmly planted in the same toxic soil that has left you feeling so disconnected. You could take the lead on planning an adventure for just the two of you as a chance to reconnect and pose that you take turns getting creative with opportunities for spending time together once a week or once every other week. These unique opportunities to spend time together could prove fruitful.
Now on the the gloomier part...After 48 years of marriage and what seems like longstanding patterns, lasting change does not often come easy. If your wife is the type to refuses to accept fault, is resistant to change, puts blame elsewhere, is dismissive, etc. then she may not be the type who will ever bend. So as much as you want her to change and be kinder to you, if she doesn't see the need for this nor have desire to make your relationship stronger, your efforts might be like beating your head against the wall. If I were you, I would ensure your wife knows how unhappy you are and that you wish for change. You can pose couple's counseling as one potential solution and hope that she buys in. If she rebukes this effort, then you will know even more concretely that your ultimate desires for her to change are not likely to happen and can plan accordingly whether it is by choosing to leave or stay and accept things as they are. However if she is willing to engage with you on this course to seek to change patterns in your marriage that have left you feeling hurt and useless, than here is reason to be hopeful that you can work on this together.
I hope this proves helpful for you. Marriage is tough and sometimes, even after years and years, marriages just simply can not be sustained. but often, they are worth fighting for and if you feel this is worth it, then push your wife to engage with you in the treatment your marriage deserves. I really hope it works out in your favor and remain available to you for additional questions or concerns.