The old TH problem. One of the biggest mistakes in Hiberno English (The official version of English spoken in Ireland).
However localisation will happen in every language and the habit of teeth blocking or making a TH sound like a D is ever present in Irish spoken English. Technically it’s an error but it can be endearing locally and accepted as a dialect. It happens in Cockney London English too where it comes out as a V or F
Then there some speakers who make such an effort to get it right they go too far. I was prompted to write this piece today after hearing an ad for Thompson Holidays on RTE radio 1, the biggest radio station in Ireland. The Voiceover mistakenly over-pronounced the H in Thompson.
So for the records fellow VOs ..The H is not pronounced in Thomas, Thompson, Thames, Thailand, Anthony and Thyme.