Why not though? We're going to be a development squad for at least another season as is, we're going to have 3 teenagers as part of the starting 11 at points regardless. There's no Rodri on the market, maybe we could plug a hole with someone underwhelming like Fofana or Berge, wait a year and go all-in for Wharton but competition for him will be fierce.
Having Casemiro and a young, talented DM developing his game at the same time would be fine, at least in my opinion. We're not going to be competing for any major trophies anyway, this season will be around focusing on top 4 and cup runs, the Europa is also a great opportunity to bed in young players.