This is an extremely cynical view of autographs. There are plenty of qualified experts who can properly authenticate specific signers. The trouble is usually with the understudied/newer signers.
Also, it isn’t feasible to do signings in person. There are entire countries, hell continents that these people will never do signings. Therefore buying one on the second hand market is the only viable option for most people.
This autopen example is an argument from exception. Pokemon forgeries are easily combated, it is simply a matter if PSA wants to pay for that level of expertise. Currently, items are very easy to source, as autographs are extremely young. For example, this individual doing these autopens is the same person making the Fake Staff Charizards. Therefore the combination of third party authentication + seller reputation is the safest option in any hobby.