As long as Hamas still has any hostages and is talking about how Israel/Jews must be eliminated (good luck changing their minds!), nobody will look weak.
While the characterization isn't entirely true, the generally accepted policy is to kill terrorists, not give them concessions after murdering and kidnapping people.
I'm curious, what's the value to Hamas of not releasing all hostages? Will that lead to even more relentless shelling since other countries know their people have been freed? Or what? I don't know enough about this situation or war in general to understand.
Hamas will release more hostages if their demands are met which mostly includes the release of Palestinian and Hamas associated prisoners in Israel.
Israel has no interest in negotiations or the hostages, hence why Hamas has barely been releasing any because their demands haven't been met.
Qatar, hosting some Hamas leaders and/or affiliates, has been acting as third party to negotiate the few hostage releases so far in exchange for some very small demands.