I think you are referring to the downgrade that happens when using 802.11b on a newer network. Past that the compatibility issues are not as prevalent as you mention.
Also, using wifi you can add an access point next to the device the same way you can add Ethernet as you mention. The cost should also be the same so I really don’t see a difference here.
Regarding security, wifi was in its infancy when WEP came out and hence had to be replaced but WPA2 has been here a long time and hasn’t gone anywhere. I don’t think the issues you used to have are as much of an issue anymore hence the change.
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