The marketplace addon was for c5 before layouts were added to the core and was superseded by the core layouts round about v5.4

Alternatives depend what you need layouts for. For example, if you have a tabs, accordion or slider addon that depends on layouts, there are others that do not use layouts at all.

If you have a complex page design, then create a theme page type (template) php file to lay it out using html and css in your theme.

Apart from general lack of reliability of layouts, the are also anti-responsive.

All this changed on 5.7+, where layouts are more reliable and can be responsive, but still best kept for special cases. Adding theme templates remains a better way to go if you need such across a site.

Thanks John! That’s very helpful. We have lots of different page structures (and I’d like to put more of the editing in the hands of non-programmers) so layouts were often very helpful. On the other hand, maybe CSS can help these days? I’ll take a look.