I was around in the 1980s and I remember the hype around VSTOL fighters like the Harrier and also the caustic negative crap directed at the Yak-38... like suggesting it could not perform a rolling takeoff severely limiting its payload potential.
The fact of the matter is that all VSTOL fighters of the time were terrible, the Sea Harrier had an excellent radar and in the falklands campaign got the best model Sidewinders from HATO stocks, but if Argentina had anything better than a MiG-21 they would have been in serious trouble.
A MiG-23 would have made the invasion impossible... they could operate from rough airstrips on the island and no Vulcan attack would have succeeded in the face of MiG-23s operating as air defence.
Against Harriers I would say the best weapon the MiG could have used would have been the R-23T IR guided missiles which were all aspect and would have been even more effective against the Harrier because of its fuselage side mounted engine nozzles that increased their IR signature from all angles except dead in front.
The MiG-23 is fast enough to leave combat when it wants to against a Harrier and it has excellent flight range.
In comparison the Yak-38 lacks a radar and agility and speed and is a rather ordinary fighter.
The Su-25 is not a great dog fighter either but it is a strike aircraft so that is not such a problem, it is more optimised for speed than it appears.
The Swing wing was complex but was also a good solution to the problem... it added weight to the design, but it was useful weight because it allowed customising life and drag in the entire flight envelope, whereas lift jets are dead weight except landing and taking off, but it is much more than that.
VSTOL aircraft like the harrier had swivelling engine nozzles but they were not 3D nozzles like we see on the MiG-29OVT... they were fixed... so there was high pressure piping of gas from the hot parts of the engine to the wing tips and the nose and the tail for puffer thrusters to help balance the aircraft in the hover and very very low flight speed mode where the airflow over the wings and tails was not sufficient to allow the control surfaces to have any effect.
This makes the VSTOL aircraft heavier and also very vulnerable to damage and with two engine nozzles down each side of the Harrier, or two rear side mounted main engine nozzles and two lift jets in the front the Yak-38 would be easy targets for MANPADS.... even the crappy oldest ones like the SA-7 Grail and the US equivalent Redeye... which normally needed to be fired at the engine end of a target in full AB to get a hit.
A key soluton for VSTOL would be engines with TVC nozzles so they don't need an internal piping system for puffer jets to control the aircraft at low speed, but also engines that balance the thrust front and back but can also be used in forward flight so they are not dead weight.
The problem is that any future VSTOL design will be handicapped with the demand to be supersonic and also 5th generation which is all going to add up to make it rather too difficult to be affordable.
Perhaps with new technology electric jet engines that engines on the wing tips that can rotate... with forward swept wings to move the wingtip engines ahead of the centre of gravity and have the main engines in the conventional place moved a bit forward closer to the centre of gravity too so they balance might create an opportunity to get something that works.
Another fundamental problem with aircraft like the Yak-38 and Yak-141 was that the lift jet engines just behind the cockpit blew hot air with much of the oxygen already burned up and in the form of CO (carbon monoxide) so if that hot air went in the front mounted engine intake for the main engine it would choke because there would not be enough oxygen to burn its fuel to generate heat and thrust and it would suddenly lose power which is the last thing you want when the lift engines are running because you are likely in a hover either landing or taking off so your main engine is keeping you airborne.
Engines way out on your wing tips that are electric so they exhaust is oxygen rich and presumably cold air should not effect the intakes for the main engines... more importantly the wing tip engines can be angled to say 95 or 100 degrees (ie 5-10 degrees forward) in the hover so the rear engine nozzles can be angled 85 to 80 degrees backwards so the hot oxygen depleted air being sucked through those engines will go backwards and away from the belly of your aircraft so you can have belly mounted weapon bays and centreline fuel tanks if you want.
Even more radical.... how about five engines... two side by side at the rear like the MiG-35, but with a serious forward swept wing with electric engines... due to the forward sweep of the wing they could be level with the cockpit, so two engines on the wing tips that can be rotated down or horizontally for forward flight, plus a dorsal fifth engine that does not vector... four engines for takeoff and landing and the fifth pointing forward... perhaps a simple ramjet to boost acceleration speeds....