Is My First Job’s Codebase Too Outdated?

I just finished an internship and accepted a full-time offer at the same company. I don't have any previous experience in web development, so I'm a bit uncertain about their coding practices. Is what I'm seeing normal or outdated? Here's a breakdown of their front-end stack: they primarily use Vanilla JavaScript (mostly ES5), jQuery, Bootstrap, and Google Closure. They also utilize the Google Closure Compiler for some type safety and rely on JSDoc annotations instead of TypeScript.

For example, their JavaScript looks something like this:

```javascript
goog.provide('src.js.CompanyLibrary.ui.form.AbcFormGrid');

/**
* u/public
* u/constructor
* u/param {string} id
* @extends {AbcComponent}
*/
function AbcFormGrid(id) {
abc.base(this, id);
/**
* @protected
* @type {string}
*/
this.containerClass = 'h-100';
// rest of the class
}

/**
* @public
*/
AbcFormGrid.prototype.showAllRows = function() {
const data = this.grid.getContainer()['bootstrapTable']('getData');
const length = data.length;
for (let i = 0; i < length; i++) {
this.grid.getContainer()['bootstrapTable']('showRow', { index: i });
}
};
```

They also shy away from ES6 features and do not make use of classes or modules, instead relying on prototypes and multiple levels of nested inheritance. They have created their own framework around this system, which includes a class that holds string constants used in building queries.

I'm unsure whether I'm just not familiar enough with the industry standards or if there might be some legitimate concerns about these practices. Any insights from those with more experience would be greatly appreciated!