I completely disagree...
2c-i is definately what is to be considered entheogen - personally 2c-i taught me that "i am you", which is a very basic revelation of entheogenic use of psychedelics.
recent and synthetic have nothing to do with entheogenic properties, 5ht2a agonism has! 2c-e would be an even better example for such a recent synthetic compound that no doubt is considered an entheogen by those with experience in this field...
entheogens are what you make of them, just like reality... some people can take huge doses of lsd and not have entheogenic experiences, while others reach nirvana/++++/god/flyingspaghettimonster with 5mg 2c-i or a hit of weed... that doesn't make lsd any less of an entheogen, it just shows how ignorant people can be in regard to the divine call
entheogen is a linguistic concept that stands in opposition to hallucinogen and is used to refer to the same class of substances, it just points to a different interpretation of the experiences that are brought on by these substances...