"The X33 was an attempt. Do we see today anything like trying to build a single stage to orbit rocket? Is there any money left for that? "

X-33 wasn't a attempt by people who had a clue. Rather it was an attempt by the clueless who thought it might look neat if it was built. The money for the X-33 was all used up, plus NASA dumped additional money into, then after NASA wouldn't pay any more money for this pig, Lockmart ended the program with nothing of any value to show for the +1 billion dumped into it.
If NASA had instead chosen a more boring vehicle which wasn't on the bleeding edge of reality, it's possible we might have made some progress in this area.