Coloring a tikzpicture with the overlays in the beamer presentation

I admire your courage and patience in drawing step by step, rectangles and circles using bezier curves.

If you have been able to do this, you may be interested to know that TikZ has planned to do all these calculations automatically.

For this purpose TikZ has created what is called a node. A node is a circular, rectangular or other shape containing text.

The advantage of using nodes is that tikz intelligently draws arrows that go from one to the other. That is, the arrow goes from edge to edge and does not penetrate (unless asked) inside the node.

I took the liberty (and I apologize) to delete your very nice code by a shorter code that uses Tikz nodes. But I kept your dimensions in pt.

Translated with www.DeepL.com/Translator (free version)

\documentclass[compress, xcolor=table, usenames,dvipsnames]{beamer}
     \usepackage{tikz}
     \usetikzlibrary{positioning,calc}
     \begin{document}

     \tikzset{every picture/.style={line width=0.75pt}, %set default line width to 0.75pt        
     skip loop/.style={to path={--++(0,25pt) -| (\tikztotarget)}},
     filled/.style={draw,rectangle,minimum height=30pt,fill=yellow,minimum width=50pt,rounded corners},
     unfilled/.style={draw,rectangle,minimum height=30pt,minimum width=50pt,rounded corners},
     cercle/.style={draw,circle,minimum size=25pt}}
\begin{frame}{Figure}

\begin{tikzpicture}[x=0.75pt,y=0.75pt,yscale=-1,xscale=1]

\node[cercle](initial) at (80,78.5){};
\node[unfilled,right =of initial](second){C(s)};
\node[unfilled,right = 39pt of second](third){P(s)};
\node[cercle,right =21pt of third](terminal){};
\draw[->](initial)--(second)--(third)--(terminal);
\path[blue,->] (initial)edge[skip loop]($(third.east)!.5!(terminal.west)$);


\node<1>[filled]at(third){P(s)};
\node<2>[filled]at(second){C(s)};
\end{tikzpicture}
    %\beamerdefaultoverlayspecification{<+->}
\begin{itemize}[<+->]
    \item P(s)
    \item C(s)
\end{itemize}
\end{frame}

\end{document}