Based on your shown samples could you please try following. Trying to fix OP's attempt here, please make sure to clear your browser cache before testing your URLs.
RewriteEngine ON
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_URI} !tinyMCE [NC]
RewriteRule ^([A-Za-z0-9-+_./]+)/?$ index.php?page=$1&%{QUERY_STRING} [L]
2nd solution: Or try with following rules too, please try to put ONLY one set of rules either above OR these ones at a time.
RewriteEngine ON
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^((?!tinyMCE)[A-Za-z0-9-+_./]+)/?$ index.php?page=$1&%{QUERY_STRING} [L]
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