No. If clear upgrades aren't available you go for marginal upgrades. Football is all about margins. The difference between 2nd place and a league title is usually 5 points. I honestly thought Wenger had learnt this lesson given his recent transfer dealings. You don't stick with Gibbs and Szczesny because they're cheap and can do a job. You get players with more upside even if they're not top class, like Monreal and Ospina, and then you try to improve on them too in the future. It makes a difference in the end when you add it all together.
People can think all they want that there aren't any possible improvements in defensive midfield for us, but it's a delusional opinion. It's like when the illuminati at Liverpool claim that Jordan Henderson is one of the best midfielders in Europe.