Stuck lifters aren't a problem . Worn Cam bearings are .
The engine oil pump feeds the cams oil from a gallery at the rear of the block.
The oil runs to the cam bearings in the heads and then to the tappet gallery.
The last place to get oil is the spray tube.
Pull both cam covers ,look at the condition of the cam lobes. Any that look scored or have blue burn marks mean the cams and bearing stands are shot.
This is caused by lack of maintenance.
I have two scrap engines here ,both taken from cars that were in nice condition but both suffered from poor maintenance in the engine. One had regular oil changes but hadn't had the filter changed in years. The filter had come to pieces and bits had blocked the cams oil galleries. The bottom end is still OK ( only 90 thou on the clock) . The second grabbed a cam,broke the valves on both heads wiping out the whole engine. The rockers were floating around inside the cam covers when I pulled them off.

This situation gets worse as the engine warms up as the lifters no longer get enough oil to keep them pumped up and they collapse .The valves don't open properly,the engine rattles a lot and there is no power.