"Bulky css framework" === time savings.
"Bulky css framework" is good when:
1. You are the only executor, and the fee for the project is fixed. Faster do more you earn.
2. Are you a web Studio. With frameworks you will rivet the typical sites with the speed of the conveyor. You will have competitive pricing and terms. Staff turnover is not terrible, because new developers are likely to know the framework you are using, and if not, have frameworks in most cases, excellent documentation and a huge community.
It is important in selecting the technology stack to proceed from the requirements, budget, timing, size and qualifications of the team.
Large projects often write without the use of css frameworks, in such projects, large budgets and deadlines, strong developers and high demands. If your goal is to grow to such projects, then learn to write without frameworks.