Egypt is in a politically-precarious position. I think they actually have a strong motive for turning a blind eye or at least approaching any condemnation of Israel with great tact, though they have in fact been critical of the assault on Gaza, as well as Israel banning UNWRA and other Israeli actions that have hampered the ability to deliver humanitarian aid to Gaza.
Egypt (along with Jordan) is a bordering country that has actually entered into peace agreements with Israel. So I think they are careful to express their disagreement with the war, without angering Israel too much and jeopardizing relations by highlighting or focusing on specific war crimes and atrocities.
Furthermore, Egypt is interested in maintaining good relations with the West, particularly the US which provides aid to Egypt and assists its military - partly to reward it for entering into peace agreements with Israel. The US is Israel's primary backer/sponsor and I'm sure Egypt does not want to upset the US or jeopardize the aid it too receives by coming down too harshly on Israel.
Egypt has also played a key role in facilitating negotiations between Israel and Hamas, and so in order to do this, it must maintain a degree of neutrality if it is to be trusted as facilitator for these negotiations.
However, it is absolutely unacceptable - from the Egyptian position - to simply open their borders and allow all the Gazans into Egypt. This, by the way, is not just Egypt's position but the position of many Western countries as well.
The reason, is that it would reward Israel's attempts to forcefully displace and ethnically cleanse Gaza - an intent that various Israeli ministers make no secret of, even publishing proposals to re-settle all of Gaza in the Sinai or Egypt so that Israel can take Gaza for itself.
This would be catastrophic for any hopes of an independent Palestinian state, and would create a situation where Gazans would not be able to return to Gaza after leaving it.
Israel denies them the right to even return to the land they were originally displaced from. What guarantee is there that they would be allowed back to Gaza after the war?
Because Egypt (along with the international community) still maintains a policy of someday hoping to achieve a 2-state solution, they cannot be the ones to be complicit in Israel's attempt to permanently end that dream by playing into Israel's hands and facilitating Ethnic Cleansing and forced displacement.
Egypt is not the country that seized and occupied Gaza. It is under Israeli control. The welfare (or lack thereof) of the people on that land is Israel's responsibility (or failure) as the occupying force - not Egypt's.
