Mate, air defense are no replacement for air power. Air defense as the name imply meant that your on the defense. When you are on the defense, that imply that initiative will be on the attackers, while you're compelled to wait for the attack which could come anytime without warning.
The biggest downside for Bangladesh has always been it's understrength air force. If Dhaka could secure just one squadron worth of truly modern 4th gen jet, then the equation will tilt once more to Bangladesh.
Not what we see in Ukraine war.
Ukraine has 1/10th the AirPower of Russia but has air defences to balance the equation.
I agree that a single squadron of 4+ ven fighters will allow BAF to take on MAF.