Lewandowsky and Benzema are players who are still productive even though they are 34 years old I think they are old but they can still score more goals in LaLiga and Benzema has carved out a lot of his name, old age is no longer an obstacle for him the most important thing is a big club like Real Madrid and Barcelona still want him to keep playing at their respective clubs to be a great competitor.
You need to understand that old age never becomes an obstacle for skilled/quality players. Benzema and Lewa are experienced and skilled strikers, they know well how to score and execute every goal opportunity. That's why both players are the mainstay player or machine goals, both for Real Madrid and Barcelona. Sure, they will score more in La Liga, I am optimistic that the scorer this season should be Lewa or Benzema.
I think if he is concerned about the performance of the game for players who have an old age it is very reasonable because logically as age grows, the energy they have decreases, if you imagine when the player is aged 20-25 then it is very different, because that age has performance the good one.
Players become more skilled and experienced as they age. There is no doubt about it. But what players start to lose as they age, is speed. And in a game like a football, speed is essential. Lewandowski and Benzema can still perform well because their fitness is still good enough. But gradually their performance will be slow. Experienced players like them may not be in the squads of Real Madrid and Barcelona. But if the main player of the team has low speed, he will not be able to adapt well to the rest of the team. Its bad effect will be seen in the overall performance of the team.