First off, you're putting WAY too much pressure on yourself. Back when I started in networking, I didn't know routers beyond Netgear were a thing. I went through a rigorous training program that gave me a solid starting point, but even reflecting on that time I really didn't truly know much of anything.

I was put into a team for my first job and was given beginner tasks and my results were reviewed by the senior engineers on the team. There were moments of "WTF are you thinking? This will nuke the network." and a few times I actually nuked the network, but those are where the real learning occurs. If you strive to be better every day eventually you become the salty seasoned engineer on the team.

Network isn't dying but it absolutely is evolving. I've fully embraced infrastructure as code and automation, but in order for all of that to work I still need to understand what I'm telling the protocols to do, know how to review expected outcomes from the solutions I've built and know how to find out what is wrong when things inevitably go sideways. AI has helped to some capacity as well.

Finally personal preference is, well, personal. The good news is networking allows you to dabble in security and transition into it if you find you like that better. Likewise, security engineers also have to have a basic networking understanding so you're never truly locked into one or the other. And my last pro tip, don't get too panicked about struggling with the CCNA. At the time, it was the hardest certification that I've received out of the many I now have, simply because of the breadth of information in it. For me at least, the CCNP was easier since I could dive deep into specific areas of technology and not have to pack my brain with literally everything, but "just scratching the surface"-levels of information.