Fine, if you believe that Dele will not score or assist many goals from now on, that's your prerogative.
However at age 23 (Dele's current age) he's trounced Lampard and Gerrard's goal/assist record despite them both having played a fair number of PL games by that age - and in each of the seasons they did play neither Lampard nor Gerrard scored many (hence their totals were low).
At aged 20 Kane had scored more goals than Rashford, but in a combination of EFL and PL games. The difference is that Rashford had played a lot more PL games aged 20 than Kane and scored more goals.
However in Kane's first (almost) full season of playing PL football Kane overtook Rashford's total.
So your comparison is just misleading - if Kane wasn't playing PL games he couldn't be scoring PL goals. All 3 of Lampard Gerrard and Dele had played plenty of PL games by age 23 - but only Dele was scoring and assisting regularly