The wing lift formula shows that lift of a wing is proportional to its area.
$$L = {\frac1 2 \rho V^2 S C_L}$$
$L$ = lift, $\rho$ = density of air, $V$ = velocity of an aircraft, $S$ = wing area, $C_L$ = coefficient of lift.$ L = {\dfrac 1 2 \times \rho V^2 \color{magenta}S C_L} {\small \begin{align} &{} &&\text{where:} &&L = \text{lift,} &&\rho = \text{density of air,} \\ &{} &&{} &&V = \text{velocity,} &&\color{magenta}S = \text{wing area,}\\ &{} &&{} &&{}&&C_L = \text{coefficient of lift.} \end{align}} $
So why are most conventional wings shaped the same (swept back rectangles)?
Imagine a conventional airplane but with the wings shaped as 2 thin long rectangles attached to a fuselage from the cockpit until the tail with the same area as the original wing.
With all other things (like angle of attack, etc) being equal will the same lift be generated as the original wing?