Perhaps you are not aware that a GC and in house team does way more work and very diversified work that the "ONE job" you have written about. Just so that you know in-house teams do not outsource more than 20% of their work. The reasons for outsourcing in decreasing order of priority are as follows:

1. Lack of in-house resources due to size and speed of a transaction.
2. Requirement of an external opinion to buttress view of the in-house team.
3. Requirement of an external opinion by a counter-party.
4. Litigation matters where an external counsel is required for arguments. (note: many in house teams prepare their own plaints etc. and there is need to hire external counsel as in-house counsels cannot argue in courts due to Advocates Act and BCI Rules).
5. Expert advise on a matter where in-house team does not have expertise.

I believe that frustration of the author is from the fact that many law firms (including several tier 1 law firms) claim expertise on certain matters but when it comes to delivery it turns out they have no idea. Their expertise was based on an individual who has long moved on from the firm, or some deal/ due diligence they did a while back where they came across a similar issue. This is frankly a rampant and unfortunate practice.

Frustration might also be coming from the fact that hourly rates of T-1 Indian law firms are not very far from Magic Circle law firms, and the quality is no where close. Also in many cases it is unfair to pass on costs of learning onto a client as a law firm had claimed to be an expert on a topic and then tries to charge 100s of hours in research time as they realised they had no idea what they were upto.

For fees quoted by these firms, I find them in the habitual practice of over-promising and under-delivering. They always come up with excuses to justify their failure to deliver within the agreed timeline.

I often come across the first cuts of the draft which on the face of it are riddled with errors (typo as well as conceptual) as a result of which I end up spending half a day doing a page turn with the external lawyers, which could have been easily avoided only if someone in their team bothered to have a re-look before sharing the drafts.
What I do not understand is lawyers use market practice as a justification for their ill-thought-out and under-researched advice. When I questioned a lawyer for blatantly questionable advice on the applicable stamp duty for our transaction, I was given a list of ‘so-and-so’ of the market who in past have happily taken such views on applicable law.
Dealing with the dispute partners is a different ball game altogether. For them, everything borders on the principle of uncertainty and “you know how Indian courts behave sometimes” advice. As a GC, try explaining these to your investors or your board.
I think there is an inherent quality issue in the legal practice irrespective of the big names involved.
"Allthatglistersisnotgold;
Oftenhaveyouheardthattold...."

Yep.

Once I prepared an invoice and gave the hours consumed.

Partner outrightly told me to increase the hours by two or three times.

I did.

The Client paid.

The reality is that these law firms are stuck in a time-warp. They used to charge such inflated bills for consuming a good number of hours in the pre-internet era. However, the internet era generation needs lesser time (almost by 50%) to find out about things.

So we get things done quickly and cheaply - something the older generation is not used to.

Now their client-relations have been going on from 90s since when their bills would have made sense. They look inflated only to the present generation who is benefiting from a lot of advantages of access to faster and comprehensive information.

However, the leading law firms are not realizing this and they are stuck in their own zone.

Either they wake up and stop over-charging than what makes sense in today's time. Clients shouldn't be paying the bill for their old habits and anachronistic working styles. Else you know a new buster scruggs is out on the horizon hunting for their clients.