There are dozens of frames, weapons and strategies that are capable of clearing Lich/Sister and Steel Path star chart missions. The power creep in warframe over the years has been massive. But that means you need to be dipping into those areas of creep.
Some things like the helminth system, arcanes, and a lot of newer mods (galvanized, etc) really shoot your power level higher. You don't say what of this stuff you have or not so it's hard to give specific advice.
At a minimum your first priorities need to be unlocking helminth and the key powers from it (ie, gloom, roar, and a few others).
Get the galvanized mods from arbitration and get them max rank.
Do not ignore your operator. The operator is stupid powerful for certain things. Farm focus and get the good arcanes and have a meta amp.
Get at least one meta weapon. My advice is target a kuva weapon or two or three. Tonkor or Zarr or Hind or Kohm or Tenet Flux rifle or Tenet Plasmor or etc. Invisibility trivializes Liches and Sisters... I have killed many of them with Ivara and the Spira prime. It is slow but very effective.
The sporelacer kitgun secondary is stupid powerful. Honestly I could use that and nothing else ever it's so good.
Tanky frames are good. The meta craps on Inaros for good reasons because he can't scale past level 300... does that matter to you when he's absolutely unkillable at level 120 (using gloom)? Same can be said for Grendel, Atlas and many other frames with a damage resistance mechanic (Citrine, Gara and so forth).
You need armor strip and there are plenty to choose from. Frost is awesome right now. Several helminth abilities give access to this for all frame. Pillage and Shurikens with augment as two examples. Unairu focus tree is another good one.
Figure out what arcanes are more or less mandatory and target farm them. Primary/secondary merciless and deadhead are must haves now. Those imply you've scaled up to killing acolytes on the steel path. Running the alerts on public is a good way to get started, but if you are set on solo then pick an easier exterminate or capture and just poke along through the mission long enough for the 5-minute spawn. Again Ivara or Loki or Ash can be slow but effective options. Or just be like me and Inaros + Tonkor all day long.
Those are not the only arcanes you want though. There are many good ones from Cetus, Fortuna, Zariman, the OG bunch (grace, energize, avenger, etc, etc).
That should be plenty of general ideas to chew on. If you have specific question always feel free to ask.