First, looking at it from a purely financial perspective, "Don't have kids" is good, not "the worst" advice (see https://themakingofamillionaire.com/is-raising-children-really-so-costly-super-expensive-says-research-5d39eaf6660).

Having said that, not only does having kids have enormous non-financial benefits, but from a societal perspective, if none of us have kids we're doomed to die out as a species.

Second, advice to not buy expensive clothes can actually be very good advice. If the expense is to pay for branding, and especially for "designer name" clothes, it will most definitely hurt your finances.

So, no, expensive clothes aren't necessarily "forever" as you say. And if you buy them to look fashionable, even before they fall apart you'll likely stop wearing them because fashion changes.

Again, as above, things aren't one-sided. I have a pair of really well-made and relatively expensive winter boots that I bought in 1995 and are still serving me much better than cheaper boots would have done before falling apart.

The bottom line here is to assess whether you're paying for durability or for fashion and/or brand/designer name. If the former, you're likely better off to buy more expensive items (assuming you can afford it in the short term). If the latter, know that it's financially less savvy, but if your finances allow it, you can still choose to buy expensive, because finances aren't and shouldn't be the be-all-and-end-all of every decision we make.