Although many Welsh people believed Iolo Morganwg's claims regarding the antiquity and authenticity of the Gorsedd, many, even from among his contemporaries, were less gullible, including:
- John Walters (1721-97), who called it 'a made Dish'
- Edward (Celtic) Davies (1756-1831), the author of a book on Druids
- William Williams, Llandygái (1738-1817) who claimed that 'no vouches can be produced (for it) but the brains of Iolo Morganwg'
- J. W. Prichard, Plas-y-brain, Llanbedr-goch (1749-1829) who detested Iolo because he was 'always a mischief-maker … making up some lies to try to deceive the world'
- Thomas Stephens (1821-75) who criticised the druidic and gorsedd institution in the periodical Yr Ymofynnydd, 1852-3.
Then, towards the end of the nineteenth century, university scholars and academics began to express their doubts:
- John Rhŷs (1840-1915), a Celtic scholar who was appointed the first Celtic professor at Oxford University in 1877, described the Gorsedd as 'antiquarian humbug, positively injurious to the true interests of the Eisteddfod'
- John Morris-Jones (1864-1929), Professor of Welsh at University College of North Wales, Bangor from 1895 onwards. In a series of five scathing articles in Cymru 1896, he cast doubts upon the alleged authenticity of the Gorsedd and came to the (erroneous) conclusion that the ceremonies had been introduced by Glamorganshire poets during the seventeenth century. He continued, 'it is all but child's play'.
- G. J. Williams (1892-1963), Professor of Welsh at University College, Cardiff from 1947 onwards. Through his meticulous research into Glamorganshire traditions and Iolo's own history he totally undermined the credibility and antiquity of the Gorsedd in an article in Y Llenor, 1922. It was, for him, 'a refuge for quackery', and its members 'merely useless members of an institution based upon falsehood and upheld through arrogance and ignorance.' Yet, he was willing to concede that 'a modern institution can be a blessing to a nation.'