So the question is in the title.
If a switch does not support Virtual Local Area Network capabilities can it still be considered a managed switch?
What other features should it have to be considered managed switch besides VLAN capabilities?
Yes. A managed switch is a switch you can configure in some way or other. Whether it supports VLANs or not is not the question. Even a switch (or a hub for that matter) that only provides status information can be considered "managed". However, the vast majority of managed Ethernet switches do support VLANs.
There are countless other features than can be configured on a switch, e.g. port parameters (duplex, speed), PoE, LACP/LAG, spanning tree, ACLs, routing, authentication, access, multicast/IGMP, QoS, MVRP/GVRP, SNMP, SPAN/mirroring, ...
Even devices where you can barely configure a thing can be called "managed". In the previous millenium I used managed HP EtherTwist repeater hubs(!) where you could do little more than configure the IP interface and check some counters for collision, jabber and such.
Yes, "manageable" obviously refers to the fact that you can manage the switch, rather than to one specific feature such as VLAN.
Among other things, some useful features such a switch could have:
The last two are less likely to be present on a non-VLAN capable switch since they are quite advanced features and one would expect VLAN capabilities on a switch that already provides those kinds of features.
This said, most manageable switches are actually VLAN-capable.