This is off topic, but there is increased risk due to the failure of the central engine and the inability to jettison it in the event of a fire.

Wikipedia notes it as a design issue: https://en.wikipedia.org/wiki/Trijet

There are documented cases where failure of the central engine has caused a loss of the rear stabilizer. This can be resolved via additional engineering -> which increases cost of manufacturing and maintenance (which as you note was the main factor in why they went away).