The staff know that getting everyone back into the correct seats will take a massive effort, so don't bother.
I strongly prefer aisle seats. I once had a girl ask me to switch seats with her so that she could sit next to her boyfriend. Since she had a middle seat, I politely declined, explaining that I would only switch with another aisle seat. She proceeded to throw a fit, calling me an asshole, etc, etc. I paid extra (how have we even come to this?) to be able to pick my seat, I'm not going to give it up for free.
Don't let people bully you.
If the local authority (flight attendants) won't back you up, you are at the discretion of whoever is hogging your seat. Any display of power over the other usually amounts to potentially being able to resort to violence if necessary to back up your power. The person in the seat know full well that you cannot do that without being forced to leave the plane, so they have effectively nothing to fear from you.
Haven't been on a Ryanair flight for a while but this certainly didn't seem to be the case when I was flying with them regularly. Was this something that's changed very recently or maybe it's only certain routes this happens on?
Parent A flies without child on Day 1; Child is given to airline by Parent B on Day 2 and retrieved on the other end by Parent A. Parent B flies without child on Day 3.
If you're upset about the money wasted on extra tickets, that's a wealth complaint not a childcare complaint.
The benefits are that your kid is then in an environment they are familiar with and they can’t just wiggle out. The downside is that you now have to lug around a car seat in the terminal. Ours got stuck in an X-ray machine once. That was fun.
I assume that’s still possible, it’s been a while since we had to travel like that.
https://www.ryanair.com/gb/en/useful-info/travelling-with-ch...
Ryanair has now accustomed Europeans to travel separately from their family, so it wouldn't surprise me to see that requirement change if it drops the price.