I agree to some extent, It's very easy to manipulate the transfer market with certain add-ons or installments or even go as far as bankrupting your club and wait for the board to inject some cash and do it over again.
But some of the stuff is very realistic, especially about add-ons. I remember how Atlético Madrid tried to maneuver around some add-on to pay less to Barcelona for Antoine Griezmann and Barcelona tried to do the same with Coutinho so they would not have to pay 20 mil to Liverpool.
I just ignore all that and buy all my players straight up with cash upfront, no add-ons, no installments. The only "crutch" I use from time to time to manipulate my budget is loan with an optional or mandatory buy fee despite it being a very common practice IRL I use it rarely.