> I have never yet had a client who even mentioned rendering speed

Because they rarely know about it. And why would they? It's a very technical choice. Factoring in things like render speed is your job when picking the most appropriate solution for the problem at hand. When you're doing this you are placing your own comfort and ease above that of anyone using the site. Google already factors site speed into rankings and with all the Web Core Vitals stuff they've been pushing lately it's only going to be more important. You're failing your clients.