I never saw the point of magnetic plugs.
They catch only the steel pieces and most of those would be picked up by the filter anyways.
Any bigger pieces will get swept away by oil flow anyways.
One of the reasons that wet sump motors last longer is that crud can settle to the bottom of the sump, out of harms way, and stay there.
When I first removed the sump from Sanji's motor there was about 3mm of metallic sludge at the bottom and this was after running Wynns Engine Flush in the oil for the last 50 miles.
I cleaned it out with solvents and some 10,000 miles later when I did gearbox rebuild #2 the sump was still clean but the 3rd time it had about a 1mm film.
Otto's motor has 160,000 miles and has never had anything other than Wynns every 4th or 5th oil change since I bought him @ 82,000 miles.
I change oil and filter every 6,000 miles and use unbranded semi-synth 10W40.