Is it worth working as a freelancer to abandon cross-browser layout in favor of new css technologies?

Question

Freelance

Is it worth working as a freelancer to abandon cross-browser layout in favor of new css technologies,
such as: css variables, object-fit, flexbox and possibly css grid.
According to statistics on caniuse, css variables are the worst supported here, 90% global and 80% Russian Federation,
does this mean that 20% of traffic from the Russian Federation will be lost due to non-crossbrowser compatibility?
Who has experience, what do customers say about this and how many failures?

Answer 1

In fact, you need to clarify with the customer what the target audience of the site is. But I abandoned IE below version 10, and even in version 10 I just try to make the site functionality work, and you can use the site at least somehow (without any effects).
It seems to me that 80% for the Russian Federation is still not enough, at least 85% is needed (including partial support). For example, flexbox can already be safely used, but css grid with caution.