Why is Another Referendum Undemocratic?

Government Timescale

06.05.2010 - General Election
             Cameron / Clegg Coalition
2011 - Fixed term parliament Act - Elections after a full 5 year term
07.05.2015 - General Election
             Cameron Government
23.06.2016 - Brexit Referendum - After 1 year
13.07.2016 - May Government - Not elected
08 06.2017 - General Election - After 2 years
             May Government 
24.07.2019 - Johnson Government - Not elected
12.12.2019 - General Election - After 2 1/2 years

The point I'm making is why, in the face of blatant disregard of their own legislation for fixed term parliaments, do Tory Brexiteers say that another referendum is not democratic? 

Also why is it in any way democratic to have unelected Prime Ministers, who obviously do not have any mandate to run the country? 

On top of both those points there's Briefing Paper 07212 of the 3rd June 2015 which says in Section 5:-

"(This Bill)does not contain any requirement for the UK Government to implement the results of the referendum, nor set a time limit by which a vote to leave the EU should be implemented. Instead, this is a type of referendum known as pre-legislative or consultative, which enables the electorate to voice an opinion which then influences the Government in its policy decisions". 

"The UK does not have constitutional provisions which would require the results of a referendum to be implemented"

So to my mind the mess we are in has nothing to do with the Democratic rights of the people. If the Government can ignore Democracy to the level they have, there must be some other reason for the 3 years of complete mismanagement we have endured.

It seems to me that the only reason that we are not having another Referendum, in the light of all the new information we now have as to the real effects Brexit will have, is because of the polarisation & in-fighting in the Conservative party.

If I'm right Democracy in any shape or form has completely gone out of the window. 

What makes matters even worse is that some Conservative MP's & Ministers have been doing very well indeed out of all this. The obvious one is Jacob Rees Mogg, through his company Somerset Capital Management.

"A plague on all their houses" I say - They should be ashamed. The Institute for Government says that the the total amount spent over the years leading up to formal exit could be as high as £2bn.