Unit test vs Integration Test vs End to End Test

I just had an interesting discussion with my team lead, he's a great guy and we're working on a pretty large and old codebase with very little unit test. I've been writing quite a lot of it whenever I have the time in the past 8 months but our product still has a looooooot of system talking to each other and unit test are not covering near half of our codebase.
They are talking about writing automated end to end test for everything possible on the UI side, thinking it is going to be more useful and provide more value in the same amount of time as writing the unit test.

To me, it seems that writing end to end test for 10% of the use cases is more expensive than writing unit test for these same 10% (in every system involved obviously) and also less maintainable.

Do you have any opinions?
I'm all for writing both unit test and integration test and end to end test but I thought that a general consensus was that unit test were far more important (even though customer's satisfaction is the most important criteria we all agree on) and also way cheaper.
Did that change with the new AI or tool available?

Thanks!