The ($1 Billion Budget) TV Show Couldn't Afford A Decent Artist To Design A Balrog
They copied 90% of the John Howe artwork :
https://www.deviantart.com/wld0graphic/art/The-Balrog-in-PJ-movies-and-Amazon-Prime-TV-series-924871603
I know that Amazon has moved production from New Zealand to the UK for financial reasons, but hiring an illustrator should be affordable for a corporation that ranked as richest company in the world.
There are even professional artists (individuals and groups) who make creative work and their products are not expensive. Here are examples:-
https://www.deviantart.com/ironshod/art/Balrog-40128157
https://www.deviantart.com/gruncirius/art/Balrog-251895469
https://www.deviantart.com/austenmengler/art/BALROG-809499457
https://www.deviantart.com/danielgovar/art/Balrog-and-Gandalf-767831413
https://www.deviantart.com/avvart/art/VS-651518688
https://www.deviantart.com/istrandar/art/The-fall-of-Durin-s-bane-827596196
https://www.deviantart.com/0oki/art/Balrog-854159423