More up-to-date alternative for "avoiding something like the plague"?

If you are going to use an idiom, or simile, go ahead and use "avoid [something] like the plague".

"Avoid [something] like the plague" is an idiom that is commonly understood. There is nothing that I have thought of, or seen suggested here, that carries the same connotations, or would be as widely understood as "avoid * like the plague". Trying to use something else as a replacement for "plague" is effectively attempting to create your own idiom. We all know what "the plague" was and that we want to avoid it.

People don't need the thing which is stated as what we are to avoid to be something that is/was more immediate to them. If this was the case, then the "Spanish Flu", or just "Flu" would have taken hold in the 1920's after 500 million people were affected by it worldwide. Google Ngrams does not find any uses of things similar to "avoid * like Spanish Flu", or "avoid * like flu", whereas "avoid * like the plague" clearly has a reasonable amount of usage.

My expectation is that when people read/hear "avoid * like the plague", a significant number are including an interpretation of the idiom as if it was stated as "avoid it like a plague", where plague means any of (merriam-webster.com):

1.   a : a disastrous evil or affliction : calamity
     b : a destructively numerous influx

2.   a : an epidemic disease causing a high rate of mortality : pestilence

rather than just specifically "the Plague":

2.   b : a virulent contagious febrile disease that is caused by a bacterium (Yersinia pestis) and that occurs in bubonic, pneumonic, and septicemic forms —called also black death

Thus, the idiom, "avoid * like the plague", already allows people to substitute in, in their own minds, whatever thing they feel should be avoided.

Using something other than "the plague" sounds, to me, made up or forced. If that is what you are trying to convey in what you are writing, then go ahead and use something else. If you are trying to use something which feels natural when people are reading/hearing it, go ahead and use "avoid * like the plague".

The articles say not use the cliché, not just to update it

What the articles which you linked in the Question are trying to say is not that you should use a different cliché-like phase in place of the cliché you are replacing, but that you should reword, or re-think, what you are writing so that you don't end up at a point where using the cliché feels like the correct phrase. Ultimately, the point of those articles is not that the cliché should be updated to something that is more relevant to the audience, but that neither the cliché, nor an updated version of it, should be used.

Hat tip to WS2, who posted as the first comment on the question that "avoid [something] like the plague" does not need to be updated.

I would consider using "avoid like anthrax". Anthrax became quite popular after the news that it was tested and used in Iraq by the Saddam Hussein regime and letters loaded with the biological weapon anthrax began surfacing in the US.

Concentrated anthrax spores were used for bioterrorism in the 2001 anthrax attacks in the United States, delivered by mailing postal letters containing the spores. The letters were sent to several news media offices and two Democratic senators: Tom Daschle of South Dakota and Patrick Leahy of Vermont. As a result, 22 were infected and five died.

I just Googled its usage by typing in "avoid like anthrax" and it seems to be used.

I don't want to tell you what to do, Zoot, but I think Tommy Lonighan is a gangster and a racist prick who you ought to avoid like anthrax.

[JAMES LEE BURKE – THE ROBICHEAUX COLLECTION]

"Avoid like ricin" and "avoid like sarin gas" seem to be used, too.

I avoid X like I avoid taxes. Wikipedia.

Tax avoidance is the legal usage of the tax regime in a single territory to one's own advantage to reduce the amount of tax that is payable by means that are within the law. (emphasis added).

I added emphasis in the definition to distinguish tax avoidance from tax evasion, which is illegal.

Tax evasion, on the other hand, is the general term for efforts by individuals, corporations, trusts and other entities to evade taxes by illegal means

One simple tactic of tax avoidance (or, more precisely tax deferment): Open an IRA. The money put into the IRA is taxed only when you withdraw it, years down the road. Moreover, your income and income tax rate may be lower after you retired than before. Other tactics: Postponing income from what has been a high income year to what you know will be a low-income year with hence a lower income tax rate. Bunching deductions in one year to overcome a floor on allowed deductions. Making a charitable deduction of appreciated stock rather than cash. Taking a vacation in s state with no sales tax and making major purchases there. There are more elaborate schemes, all legal, but requiring much more work to pull off, and more money to make them worthwhile.

A somewhat updated version is avoid it like the clap. I say "somewhat" because the clap sounds very 1970s to me; I guess you could say avoid it like an STD but that doesn't have quite the same resonance, and avoid it like gonorrhea is kind of TMI. (Definition of "the clap" from The Free Dictionary's Medical Dictionary here.)

Some examples of usage:

avoid it like the clap. (Yelp list of "places to avoid... well... like the clap".)

The other rule is: Ask yourself, “Would a partially toothless hooker named Whistles enjoy this trend?” If so, avoid it like the clap. (Clinton Kelly, Freakin' Fabulous: How to Dress, Speak, Behave, Eat, Drink, Entertain, Decorate, and Generally Be Better Than Everyone Else, 2008)

Avoid it like the clap. Unless you like the clap. Then this place may be for you. (Topix review of a haunted house, by user "It burns")

Avoid it like poison also gets quite a few hits, as seen here and in this ngram. It's a classic, though I don't know how much of a punch it packs. I suspect most of us today only really think about poison when our toddler somehow manages to drink a half-full bottle of perfume when we looked away for, like, twenty seconds or when we're trying to figure out how to get rid of pests.

Personally, for a real 21st century squick-factor I might use

Avoid like bedbugs

This is a problem that is plaguing (sorry) hotels, colleges, and the like, and individuals are taking measures like checking online registries and mattress corners to try to avoid them when they travel. I would link to articles on the subject, but I try to avoid pictures and stories as much as possible.