How so? I am in the industry and everyone I work with take them seriously.
Edit:
Even if you refute predictions made by the IAE, nuclear is still not as expensive as other sources of electricity. For a more specific example, the University of Waterloo released this report analyzing the Ontario grid in 2017.
If you look at Table 1, you will find that nuclear costs between hydro and wind while gas and solar cost more. This is one example but it does illustrate that nuclear is not necessarily the most expensive. Things have improved for renewables since then but I believe they have for nuclear also.