There are antisemitic criticisms of Israel and there are anti-colonialist arguments against Israel. I wouldn't disagree that a lot of people fall in the trap of using the former (if they don't do so deliberately) but the latter certainly exist and don't require any naivety about international relations.

Claiming the Israeli government is actively and deliberately harming a group of people and defying international agreements to pursue distasteful goals is not a naïve view of international elations and doesn't require believing there is a meaningful category of "good" and "evil" actors.

The problem with the argument for the foundation of Israel (if we ignore the specific historical and religious claims for the area it is located in, because that's a whole can of worms) is that the nature of Israel is entirely different from the nature of any other post-colonialist state.

Usually how this works is that we have a population living in an area over a long period of time, then a (usually white European) population conquers the region and establishes its own settler government while its own population expands and the pre-existing population is treated as second class citizens or fully disenfranchised. Liberatory struggle is easily justified in a situation like this because in order to restore the rights and political power of the original population the new population must be removed (either physically, or at least from political power, but in effect this will often involve repossession of illegitimately claimed territory, capital and wealth). The consequence can appear as an ethnostate or Apartheid regime with the original colonizers temporarily becoming an apparent "underclass" until the original population has established a new power structure that can accommodate them without reverting to the previous system (e.g. because the previous ruling class still holds all capital despite having formally ceded its political power).

The problem with Israel is that this isn't how we got here. There was a small minority of Jewish people in pre-Israel Palestine and there were Arabs (and other groups) in pre-Israel Palestine, but there wasn't one group acting as a "colonizer". The groups were all already endemic and well-established. What happened instead is that some people holding claims to land sold their land to a group intending to found the state of Israel in that territory and with the help of international political and financial supporters a new nation state was established and non-Jewish people already living in the land were evicted by the people now claiming ownership over their land -- this process is in fact still ongoing. Additionally Israel being envisioned as a "Jewish nation" enacted policies granting non-Jewish residents fewer rights while actively promoting immigration and easy access to citizenship for Jewish people living in other countries. But as even some Jewish people have pointed out the Israeli government tends to favor "white Jews" over Jewish POC and e.g. heavily promoted Hebrew for political reasons despite Yiddish initially being far more widely understood and established.

So the argument for the legitimacy of the modern state of Israel (if you ignore the religious/historical argument or an argument of might makes right) hinges on how legitimate the original "sale" of Palestinian land to the Jewish settlers was, which is a question with no clear answer. And that's just the question of legitimacy, not even getting into any of Israel's behavior since that point.

Now, even if you think the original land claims justify the expansion of Israeli settlements into autonomous Palestine and the eviction of Palestinian residents in those areas, and even if you see no problem with the quasi-Apartheid second class citizenship of Palestinian Arabs in Israel, and if you don't think any of the claims of Israel being deliberately racist against non-white Jews are valid, there's still the issue of the Israeli state military retaliating against terrorist strikes by bombing civilian targets. I guess where you stand on that issue depends on whether you agree with the US's definition of any male of fighting age in a "war zone" (i.e. by definition wherever a drone strike happens) being a "combatant" unless proven otherwise, but that is a highly contentious issue when it comes to US drone strikes so it's easy to see why people might have strong opinions when it comes to Israeli bombings.

Basically what I'm trying to demonstrate is that while "being anti-Israel" covers a wide range of very complex issues with plenty of opportunities to tie in antisemitic arguments (e.g. you could believe the land claims are illegitimate because you believe in a global Jewish banking conspiracy) you don't have to be either antisemitic or naïve to think any of these issues are legitimate concerns or significant enough to warrant opposition (and let's be realistic: "not supporting directly financing a foreign government's military" is a very low bar for "opposition").