Does high Net Income certainly adds value to company’s equity shareholders?

May be not. Because earnings available to share holders is the residual income after obligations to creditors have been availed of. Net income generated is the accounting income but shareholders are concerned of the economic value added (EVA) to the firm.
EVA is an estimate of true economic profit after adjusting for the opportunity cost of equity capital.

EVA= NOPAT - $WACC

NOPAT= Net operating profit after tax
= (Revenues- COGS- SG&A-Dep)(1-tax)
= EBIT(1-tax)
= Net Income +Net Interest Expense (1-tax)
$WACC = Weighted average cost of capital in dollar terms
= Capital employed * WACC