Overall, I'd say even though he is obviously declined compared to his prime days, it is not that easy to find strikers that score 30-35 goals per season.
You can generally do with less of a high-scorer at no9 position, if you can distribute the goals among 4-5 players. Say you have some excellent wingers, and a top box-to-box that can chip in with 10 goals from midfield, like Lampard used to do. But if your wingers and midfielders don't have much end product, and I'm talking mostly about goal-scoring prowess here, the no9 is gonna have to score often.
Arsenal is a good example. Odegaard scored 15 goals last season in the league. That's a huge number for an AM. You can go down that route, but looking at our midfielders, and I'm not seeing much goal-scoring potential like that.
Point is goals have to come from somewhere. Be it mainly from a high-scoring no9, or somewhat evenly distributed between top energetic forwards and CM-AMs that work hard off the ball to get to the end of chances despite playing farther away from goal compared to a classical no9. In the absence of a 9 that can score 30ish goals a season in all comps, you need most of your attacking options to chip in with some 10 goals each.
Once Lewa is gone in 1-2 seasons, a lot of burden is gonna be put on likes of Roque, Yamal, Raphinha, and whoever is left in AM, winger, and 9 positions. Together they will need to make up for 30-35 goals.
Or the club is gonna try to sign another old, formerly-elite, striker, and pay him a big salary for a shorter contract. Maybe Kane once he reaches 34 as well.