Every and any decision is a form of lock-in. The decision to buy on-brand or off-brand, open or closed source, vendor A or vendor B has consequences that follow.
A decision to do nothing also creates lock-in to the solution you already have.
Everything is a lock-in one way or another.
That doesn’t make lock-in irrelevant as a design criteria. Far from it.
In my view, your design should deeply consider how to difficult/expensive/costly it will be to undo/reverse/replace the decision.
Any decision can be changed or reversed. Technology changes, best practice becomes legacy practice, new solutions do it better/faster/cheap.
Therefore the key factor is lockin in design is to understand the cost of ‘un-design’ and what is will take replace the lockin.
More simply, the most important aspect of decision making is to understand the consequences of that decision. Lockin is guaranteed one way or another but the goal is to reduce it to the minimum so that you can undo.
The EtherealMind View
Using this way of thinking means it can be ok to use a proprietary technology so long as the cost of throwing it away is small, quick and painless. The obverse is that a vendor selling you a complex, expensive and hard to remove solution is locking you in.
Note: Reversing or changing decisions is a DevOps thing. A DevOps based network encourages faster decision making by reducing the cost of making the decision but also the cost of undoing if doesn’t work out.