I wouldn't say that is the only problem. If they miss one or two games, what games are they missing?Strangely enough the two players you mentioned did get covid last season. Both only missed one game. For most players getting covid means they won't be available for one or two games. That is less than the average minor knock sidelines a player for. Only problem is if your whole team catches covid at the same time, but even then usually the league or FA postpones your next game anyway.
Also if they catch covid, how do they handle it? Some players are fine some are really affected for a long period. Think about Gabriel and Aouar is an example last season.
The need to have 2 players for every position is greater than ever.