I agree with Ditz and HP that you are far from a failure. It is your skids and your bride that are the issue, not you.

I believe that the issue is your wife's because she tolerates the rude and dismissive behavior of her spawn. We learned that the only way to keep my Skid's brain engaged was to take his phone. Even now that he is 21, serving in the USAF, and paying his own phone bill we do not allow him to take out his phone when we are together. It is rude and when he does it either my bride, or I, or both of us tell him to put it away or leave. He has yet to call that ultimatum.

When he turned 18 we took a family road trip from OR to TX when we went to pick him up from his final court ordered Sperm Land visitation. The first day he spent the whole time on his phone. So we took it and made him drive much of the remaining two thousand miles of that trip. Interestingly he appreciates that we forced him to engage and experience the amazing things we saw and did on that trip.

I would suggest that your bride institutes an unequivocal law that when her children walk in the door of your home their phones go in a basket on mute. If they touch their phone while they are ini your home the phones gets turned off and locked up until they are walking out of the door.

If your bride won't step up and enforce this rule then you do it and she can bite her lip. She has a choice, step up, parent and discipline before you have to or support you while you do it.

IMHO or course.
Good luck.

This probably isnt going to help but from when I was 4/5 years old I gained both a step mother and a step father. When my parents split my BM moved my step dad in and two years later I demanded to live with my dad.
Now when I was a toddler I was very much a daddys girl, not really sure why, both my parents worked full time so I didnt have more time with one than the other.
For whatever reason I was always tightly bonded with my dad and not so much with my mother. Now I was able to accept my step mother but not my step father. It took a very long time for me to be able to accept him, I would often sass him, honestly I was quite vile to him.
My mother would discipline me for being rude to him, but once I was living with my dad my visitation changed to when I wanted to visit, so at the age of 7 I had control over my own visitation times. Sometimes I saw my mother weekly, sometimes I refused to see her for months at a time. Right or wrong, thats how it was, I was always very headstrong.
One day my step father and I had an argument, and the usual "you arent my dad you cant tell me what to do" came up, he said he was glad he wasnt my father and he would never want to be. Once we had that sorted between us we were actually able to build a relationship. Only sad thing is, I was 13 years old by the time that happened. So this poor man spent the first 8/9 years with me being a complete evil piece of work to him.

No one at the time thought/felt I had any confusion over who was who, both my mother and my father explained to me when my step parents came into my life that they were not taking the place of my other parent but they were the adult and as such expected respect. Yet what worked in one household didnt in the other.

I guess what Im trying to say is it isnt you. Depending on their ages maybe talk to your step kids, the analogy of; im not your mum/dad but you can think of me like your aunt/uncle, I expect you to listen to me and follow my rules because this is my house and if you dont then there will be consequences.

But as the others say primarily you need to make sure your partner is fully supporting you. Being a step parent is hard enough, but if you dont have the proper support from your partner it has the potential to destroy you.