Learn French: Un critère économique, tel que le revenu, ne change rien. - An economic criterion, such as income, changes nothing.

The phrase tel que (such as) must agree in gender and number with the noun that comes right before it, which is the category you are giving an example of. Here, it agrees with un critère, which is masculine singular, so it stays tel que.

If the example was a feminine word instead of le revenu, would tel que change?

No, it wouldn't. A very common mistake is making tel que agree with the example itself. Remember that it always agrees with the overarching category (here, un critère), regardless of the gender or number of the specific examples that follow.

Is critère always masculine? The ending looks feminine.

Yes, un critère is masculine. Words ending in -ère are very often feminine (like la mère or la lumière), so this is a great exception to memorize. Its masculine gender is exactly why we use the masculine tel que.

Could I just use comme instead of tel que in this sentence?

Yes, you could say Un critère économique, comme le revenu, ne change rien. Using tel que is slightly more formal and precise for giving examples of a category, while comme is more versatile and frequently used in everyday spoken French.