As you're mainly complaining about CSS layout features being used here:

For a long time we were forced to use the ugliest hacks imaginable to get to the nice (responsive, design-minimalist(!)) layouts we wanted, because CSS layout tools were utter archaic bs, for years on end, because browsers iterated so slowly.

Then things started speeding up, and we're getting to make better websites (and apps!) that are way easier to design (with the correct design theory equivalents), implenent (with less code) and easier to maintain (i.e., understand). And you're not missing out if you just keep your browser up to date.

I know it sucks if you're on an unsupported device that doesn't get any updates, fair.

But let's face it: 99% of the population is better off security-wise when we're not enabling them to run unpatched devices forever.