One of my favorite concepts to teach in Economics was opportunity costs. On a surface level, the answer seems obvious. You added a player you did not add yesterday. Of course your team should be better. However, this is where opportunity costs rear their ugly head. Spending 20 million per season on Walker means you cannot spend that in other places. Unlike the Mets, Yankees, or Dodgers, the Astros do not have an unlimited budget.
Since Dana Brown swung the trade sending Kyle Tucker out of town, first and third base are ably manned by Walker and Isaac Paredes.